* sp/maint-fetch-pack-stop-early:
enable "no-done" extension only when fetching over smart-http
* sp/maint-upload-pack-stop-early:
enable "no-done" extension only when serving over smart-http
Last night I had to make these two emergency reverts, but now we have a
better understanding of which part of the topic was broken, let's get rid
of the revert to fix it correctly.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Do not advertise no-done capability when upload-pack is not serving over
smart-http, as there is no way for this server to know when it should stop
reading in-flight data from the client, even though it is necessary to
drain all the in-flight data in order to unblock the client.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Shawn O. Pearce <spearce@spearce.org>
This reverts 3e63b21 (upload-pack: Implement no-done capability,
2011-03-14). Together with 761ecf0 (fetch-pack: Implement no-done
capability, 2011-03-14) it seems to make the fetch-pack process out of
sync and makes it keep talking long after upload-pack stopped listening to
it, terminating the process with SIGPIPE.
If the client requests both multi_ack_detailed and no-done then
upload-pack is free to immediately send a PACK following its first
'ACK %s ready' message. The upload-pack response actually winds
up being:
ACK %s common
... (maybe more) ...
ACK %s ready
NAK
ACK %s
PACK.... the pack stream ....
For smart HTTP connections this saves one HTTP RPC, reducing
the overall latency for a trivial fetch. For git:// and ssh://
a no-done option slightly reduces latency by removing one
server->client->server round-trip at the end of the common
ancestor negotiation.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
If a client is merely following the remote (and has not made any
new commits itself), all "have %s" lines sent by the client will be
common to the server. As all lines are common upload-pack never
calls ok_to_give_up() and does not compute if it has a good cut
point in the commit graph.
Without this computation the following client is going to send all
tagged commits, as these were determined to be COMMON_REF during the
initial advertisement, but the client does not parse their history
to transitively pass the COMMON flag and empty its queue of commits.
For git.git with 339 commit tags, it takes clients 11 rounds of
negotation to fully send all tagged commits and exhaust its queue
of things to send as common. This is pretty slow for a client that
has not done any local development activity.
Force computing ok_to_give_up() and send "ACK %s ready" at the end
of the current round if this round only contained common objects
and ok_to_give_up() was therefore not called. This may allow the
client to break early, avoiding transmission of the COMMON_REFs.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This shows a trace of all packets coming in or out of a given
program. This can help with debugging object negotiation or
other protocol issues.
To keep the code changes simple, we operate at the lowest
level, meaning we don't necessarily understand what's in the
packets. The one exception is a packet starting with "PACK",
which causes us to skip that packet and turn off tracing
(since the gigantic pack data will not be interesting to
read, at least not in the trace format).
We show both written and read packets. In the local case,
this may mean you will see packets twice (written by the
sender and read by the receiver). However, for cases where
the other end is remote, this allows you to see the full
conversation.
Packet tracing can be enabled with GIT_TRACE_PACKET=<foo>,
where <foo> takes the same arguments as GIT_TRACE.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Add commit_list prefix to insert_by_date function and to sort_by_date,
so it's clear that these functions refer to commit_list structure.
Signed-off-by: Thiago Farina <tfransosi@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When printing an error message saying a ref was requested that we do not
have, only print that ref, rather than the ref and everything sent to us
on the same packet line (e.g. protocol support specifications).
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A bit of history in chronological order, the newest at bottom:
- 80ccaa7 (upload-pack: Move the revision walker into a separate function.)
do_rev_list was introduced with create_full_pack argument
- 21edd3f (upload-pack: Run rev-list in an asynchronous function.)
do_rev_list was now called by start_async, create_full_pack was
passed by rev_list.data
- f0cea83 (Shift object enumeration out of upload-pack)
rev_list.data was now zero permanently. Creating full pack was
done by passing --all to pack-objects
- ae6a560 (run-command: support custom fd-set in async)
rev_list.data = 0 was found out redudant and got rid of.
Get rid of the code as well, for less headache while reading do_rev_list.
[jc: noticed by Elijah Newren]
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This patch adds the possibility to supply a set of non-0 file
descriptors for async process communication instead of the
default-created pipe.
Additionally, we now support bi-directional communiction with the
async procedure, by giving the async function both read and write
file descriptors.
To retain compatiblity and similar "API feel" with start_command,
we require start_async callers to set .out = -1 to get a readable
file descriptor. If either of .in or .out is 0, we supply no file
descriptor to the async process.
[sp: Note: Erik started this patch, and a huge bulk of it is
his work. All bugs were introduced later by Shawn.]
Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This hook runs after "git fetch" in the repository the objects are
fetched from as the user who fetched, and has security implications.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* sp/smart-http: (37 commits)
http-backend: Let gcc check the format of more printf-type functions.
http-backend: Fix access beyond end of string.
http-backend: Fix bad treatment of uintmax_t in Content-Length
t5551-http-fetch: Work around broken Accept header in libcurl
t5551-http-fetch: Work around some libcurl versions
http-backend: Protect GIT_PROJECT_ROOT from /../ requests
Git-aware CGI to provide dumb HTTP transport
http-backend: Test configuration options
http-backend: Use http.getanyfile to disable dumb HTTP serving
test smart http fetch and push
http tests: use /dumb/ URL prefix
set httpd port before sourcing lib-httpd
t5540-http-push: remove redundant fetches
Smart HTTP fetch: gzip requests
Smart fetch over HTTP: client side
Smart push over HTTP: client side
Discover refs via smart HTTP server when available
http-backend: more explict LocationMatch
http-backend: add example for gitweb on same URL
http-backend: use mod_alias instead of mod_rewrite
...
Conflicts:
.gitignore
remote-curl.c
In theory it is possible for sideband channel #2 to be delayed if
pack data is quick to come up for sideband channel #1. And because
data for channel #2 is read only 128 bytes at a time while pack data
is read 8192 bytes at a time, it is possible for many pack blocks to
be sent to the client before the progress message fifo is emptied,
making the situation even worse. This would result in totally garbled
progress display on the client's console as local progress gets mixed
with partial remote progress lines.
Let's prevent such situations by giving transmission priority to
progress messages over pack data at all times.
Signed-off-by: Nicolas Pitre <nico@fluxnic.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When --stateless-rpc is passed as a command line parameter to
upload-pack or receive-pack the programs now assume they may
perform only a single read-write cycle with stdin and stdout.
This fits with the HTTP POST request processing model where a
program may read the request, write a response, and must exit.
When --advertise-refs is passed as a command line parameter only
the initial ref advertisement is output, and the program exits
immediately. This fits with the HTTP GET request model, where
no request content is received but a response must be produced.
HTTP headers and/or environment are not processed here, but
instead are assumed to be handled by the program invoking
either service backend.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
When multi_ack_detailed is enabled the ACK continue messages returned
by the remote upload-pack are broken out to describe the different
states within the peer. This permits the client to better understand
the server's in-memory state.
The fetch-pack/upload-pack protocol now looks like:
NAK
---------------------------------
Always sent in response to "done" if there was no common base
selected from the "have" lines (or no have lines were sent).
* no multi_ack or multi_ack_detailed:
Sent when the client has sent a pkt-line flush ("0000") and
the server has not yet found a common base object.
* either multi_ack or multi_ack_detailed:
Always sent in response to a pkt-line flush.
ACK %s
-----------------------------------
* no multi_ack or multi_ack_detailed:
Sent in response to "have" when the object exists on the remote
side and is therefore an object in common between the peers.
The argument is the SHA-1 of the common object.
* either multi_ack or multi_ack_detailed:
Sent in response to "done" if there are common objects.
The argument is the last SHA-1 determined to be common.
ACK %s continue
-----------------------------------
* multi_ack only:
Sent in response to "have".
The remote side wants the client to consider this object as
common, and immediately stop transmitting additional "have"
lines for objects that are reachable from it. The reason
the client should stop is not given, but is one of the two
cases below available under multi_ack_detailed.
ACK %s common
-----------------------------------
* multi_ack_detailed only:
Sent in response to "have". Both sides have this object.
Like with "ACK %s continue" above the client should stop
sending have lines reachable for objects from the argument.
ACK %s ready
-----------------------------------
* multi_ack_detailed only:
Sent in response to "have".
The client should stop transmitting objects which are reachable
from the argument, and send "done" soon to get the objects.
If the remote side has the specified object, it should
first send an "ACK %s common" message prior to sending
"ACK %s ready".
Clients may still submit additional "have" lines if there are
more side branches for the client to explore that might be added
to the common set and reduce the number of objects to transfer.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
There were several unchecked use of fdopen(); replace them with xfdopen()
that checks and dies.
Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In 2d14d65 (Use a clearer style to issue commands to remote helpers,
2009-09-03) I happened to notice two changes like this:
- write_in_full(helper->in, "list\n", 5);
+
+ strbuf_addstr(&buf, "list\n");
+ write_in_full(helper->in, buf.buf, buf.len);
+ strbuf_reset(&buf);
IMHO, it would be better to define a new function,
static inline ssize_t write_str_in_full(int fd, const char *str)
{
return write_in_full(fd, str, strlen(str));
}
and then use it like this:
- strbuf_addstr(&buf, "list\n");
- write_in_full(helper->in, buf.buf, buf.len);
- strbuf_reset(&buf);
+ write_str_in_full(helper->in, "list\n");
Thus not requiring the added allocation, and still avoiding
the maintenance risk of literal string lengths.
These days, compilers are good enough that strlen("literal")
imposes no run-time cost.
Transformed via this:
perl -pi -e \
's/write_in_full\((.*?), (".*?"), \d+\)/write_str_in_full($1, $2)/'\
$(git grep -l 'write_in_full.*"')
Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
First of all, I can't find any reason why thin pack generation is
explicitly disabled when dealing with a shallow repository. The
possible delta base objects are collected from the edge commits which
are always obtained through history walking with the same shallow refs
as the client, Therefore the client is always going to have those base
objects available. So let's remove that restriction.
Then we can make shallow repository deepening much more efficient by
using the remote's unshallowed commits as edge commits to get preferred
base objects for thin pack generation. On git.git, this makes the data
transfer for the deepening of a shallow repository from depth 1 to depth 2
around 134 KB instead of 3.68 MB.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The majority of code in core git appears to use a single
space after if/for/while. This is an attempt to bring more
code to this standard. These are entirely cosmetic changes.
Signed-off-by: Brian Gianforcaro <b.gianfo@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
A request to clone the repository does not give any "have" but asks for
all the refs we offer with "want". When a request does not ask to clone
the repository fully, but asks to fetch some refs into an empty
repository, it will not give any "have" but its "want" won't ask for all
the refs we offer.
If we suppose (and I would say this is a rather big if) that it makes
sense to distinguish these two cases, a hook cannot reliably do this
alone. The hook can detect lack of "have" and bunch of "want", but there
is no direct way to tell if the other end asked for all refs we offered,
or merely most of them.
Between the time we talked with the other end and the time the hook got
called, we may have acquired more refs or lost some refs in the repository
by concurrent operations. Given that we plan to introduce selective
advertisement of refs with a protocol extension, it would become even more
difficult for hooks to guess between these two cases.
This adds "kind [clone|fetch]" to hook's input, as a stable interface to
allow the hooks to tell these cases apart.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
After upload-pack successfully finishes its operation, post-upload-pack
hook can be called for logging purposes.
The hook is passed various pieces of information, one per line, from its
standard input. Currently the following items can be fed to the hook, but
more types of information may be added in the future:
want SHA-1::
40-byte hexadecimal object name the client asked to include in the
resulting pack. Can occur one or more times in the input.
have SHA-1::
40-byte hexadecimal object name the client asked to exclude from
the resulting pack, claiming to have them already. Can occur zero
or more times in the input.
time float::
Number of seconds spent for creating the packfile.
size decimal::
Size of the resulting packfile in bytes.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* cc/replace:
t6050: check pushing something based on a replaced commit
Documentation: add documentation for "git replace"
Add git-replace to .gitignore
builtin-replace: use "usage_msg_opt" to give better error messages
parse-options: add new function "usage_msg_opt"
builtin-replace: teach "git replace" to actually replace
Add new "git replace" command
environment: add global variable to disable replacement
mktag: call "check_sha1_signature" with the replacement sha1
replace_object: add a test case
object: call "check_sha1_signature" with the replacement sha1
sha1_file: add a "read_sha1_file_repl" function
replace_object: add mechanism to replace objects found in "refs/replace/"
refs: add a "for_each_replace_ref" function
upload-pack runs pack-objects, which generates progress indicator output
on its stderr. If the client requests a sideband, this indicator is sent
to the client; but if it did not, then the progress is written to
upload-pack's own stderr.
If upload-pack is itself run from git-daemon (and if the client did not
request a sideband) the progress indicator never reaches the client and it
need not be generated in the first place. With this patch the progress
indicator is suppressed in this situation.
Signed-off-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Offload object enumeration in upload-pack to pack-objects, but fall
back on internal revision walker for shallow interaction. Aside from
architecturally making more sense, this also leaves the door open for
pack-objects to employ a revision cache mechanism. Test t5530 updated
in order to explicitly check both enumeration methods.
Signed-off-by: Nick Edelen <sirnot@gmail.com>
Acked-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This new "read_replace_refs" global variable is set to 1 by
default, so that replace refs are used by default. But
reachability traversal and packing commands ("cmd_fsck",
"cmd_prune", "cmd_pack_objects", "upload_pack",
"cmd_unpack_objects") set it to 0, as they must work with the
original DAG.
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* lt/pack-object-memuse:
show_object(): push path_name() call further down
process_{tree,blob}: show objects without buffering
Conflicts:
builtin-pack-objects.c
builtin-rev-list.c
list-objects.c
list-objects.h
upload-pack.c
In particular, pushing the "path_name()" call _into_ the show() function
would seem to allow
- more clarity into who "owns" the name (ie now when we free the name in
the show_object callback, it's because we generated it ourselves by
calling path_name())
- not calling path_name() at all, either because we don't care about the
name in the first place, or because we are actually happy walking the
linked list of "struct name_path *" and the last component.
Now, I didn't do that latter optimization, because it would require some
more coding, but especially looking at "builtin-pack-objects.c", we really
don't even want the whole pathname, we really would be better off with the
list of path components.
Why? We use that name for two things:
- add_preferred_base_object(), which actually _wants_ to traverse the
path, and now does it by looking for '/' characters!
- for 'name_hash()', which only cares about the last 16 characters of a
name, so again, generating the full name seems to be just unnecessary
work.
Anyway, so I didn't look any closer at those things, but it did convince
me that the "show_object()" calling convention was crazy, and we're
actually better off doing _less_ in list-objects.c, and giving people
access to the internal data structures so that they can decide whether
they want to generate a path-name or not.
This patch does that, and then for people who did use the name (even if
they might do something more clever in the future), it just does the
straightforward "name = path_name(path, component); .. free(name);" thing.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Here's a less trivial thing, and slightly more dubious one.
I was looking at that "struct object_array objects", and wondering why we
do that. I have honestly totally forgotten. Why not just call the "show()"
function as we encounter the objects? Rather than add the objects to the
object_array, and then at the very end going through the array and doing a
'show' on all, just do things more incrementally.
Now, there are possible downsides to this:
- the "buffer using object_array" _can_ in theory result in at least
better I-cache usage (two tight loops rather than one more spread out
one). I don't think this is a real issue, but in theory..
- this _does_ change the order of the objects printed. Instead of doing a
"process_tree(revs, commit->tree, &objects, NULL, "");" in the loop
over the commits (which puts all the root trees _first_ in the object
list, this patch just adds them to the list of pending objects, and
then we'll traverse them in that order (and thus show each root tree
object together with the objects we discover under it)
I _think_ the new ordering actually makes more sense, but the object
ordering is actually a subtle thing when it comes to packing
efficiency, so any change in order is going to have implications for
packing. Good or bad, I dunno.
- There may be some reason why we did it that odd way with the object
array, that I have simply forgotten.
Anyway, now that we don't buffer up the objects before showing them
that may actually result in lower memory usage during that whole
traverse_commit_list() phase.
This is seriously not very deeply tested. It makes sense to me, it seems
to pass all the tests, it looks ok, but...
Does anybody remember why we did that "object_array" thing? It used to be
an "object_list" a long long time ago, but got changed into the array due
to better memory usage patterns (those linked lists of obejcts are
horrible from a memory allocation standpoint). But I wonder why we didn't
do this back then. Maybe there's a reason for it.
Or maybe there _used_ to be a reason, and no longer is.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The goal of this patch is to get rid of the "static struct rev_info
revs" static variable in "builtin-rev-list.c".
To do that, we need to pass the revs to the "show_commit" function
in "builtin-rev-list.c" and this in turn means that the
"traverse_commit_list" function in "list-objects.c" must be passed
functions pointers to functions with 2 parameters instead of one.
So we have to change all the callers and all the functions passed
to "traverse_commit_list".
Anyway this makes the code more clean and more generic, so it
should be a good thing in the long run.
Signed-off-by: Christian Couder <chriscool@tuxfamily.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These weren't used outside and can be safely moved
Signed-off-by: Benjamin Kramer <benny.kra@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Certain remote commands, when asked to do something in a
particular directory that was not actually a git repository,
would say "unable to chdir or not a git archive". The
"chdir" bit is an unnecessary detail, and the term "git
archive" is much less common these days than "git repository".
So let's switch them all to:
fatal: '%s' does not appear to be a git repository
Signed-off-by: Jeff King <peff@peff.net>
Acked-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Programs that use git_config need to find the global configuration.
When runtime prefix computation is enabled, this requires that
git_extract_argv0_path() is called early in the program's main().
This commit adds the necessary calls.
Signed-off-by: Steffen Prohaska <prohaska@zib.de>
Acked-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This is a mechanical conversion of all '*.c' files with:
s/((?:die|error|warning)\("git)-(\S+:)/$1 $2/;
The result was manually inspected and no false positive was found.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We will need the command invocation path in system_path(). This path was
passed to setup_path(), but system_path() can be called earlier, for
example via:
main
commit_pager_choice
setup_pager
git_config
git_etc_gitconfig
system_path
Therefore, we introduce git_set_argv0_path() and call it as soon as
possible.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
In upload-pack we must explicitly close the output channel of rev-list.
(On Unix, the channel is closed automatically because process that runs
rev-list terminates.)
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
The new protocol extension "include-tag" allows the client side
of the connection (fetch-pack) to request that the server side of the
native git protocol (upload-pack / pack-objects) use --include-tag
as it prepares the packfile, thus ensuring that an annotated tag object
will be included in the resulting packfile if the object it refers to
was also included into the packfile.
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
To facilitate testing and verification of the requests sent by
git-fetch to the remote side we permit logging the received packet
lines to the file descriptor specified in GIT_DEBUG_SEND_PACK has
been set. Special start and end lines are included to indicate
the start and end of each connection.
$ GIT_DEBUG_SEND_PACK=3 git fetch 3>UPLOAD_LOG
$ cat UPLOAD_LOG
#S
want 8e10cf4e007ad7e003463c30c34b1050b039db78 multi_ack side-band-64k thin-pack ofs-delta
want ddfa4a33562179aca1ace2bcc662244a17d0b503
#E
#S
want 3253df4d1cf6fb138b52b1938473bcfec1483223 multi_ack side-band-64k thin-pack ofs-delta
#E
>From the above trace the first connection opened by git-fetch was to
download two refs (with values 8e and dd) and the second connection
was opened to automatically follow an annotated tag (32).
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* mk/maint-parse-careful:
receive-pack: use strict mode for unpacking objects
index-pack: introduce checking mode
unpack-objects: prevent writing of inconsistent objects
unpack-object: cache for non written objects
add common fsck error printing function
builtin-fsck: move common object checking code to fsck.c
builtin-fsck: reports missing parent commits
Remove unused object-ref code
builtin-fsck: move away from object-refs to fsck_walk
add generic, type aware object chain walker
Conflicts:
Makefile
builtin-fsck.c
* mk/maint-parse-careful:
peel_onion: handle NULL
check return value from parse_commit() in various functions
parse_commit: don't fail, if object is NULL
revision.c: handle tag->tagged == NULL
reachable.c::process_tree/blob: check for NULL
process_tag: handle tag->tagged == NULL
check results of parse_commit in merge_bases
list-objects.c::process_tree/blob: check for NULL
reachable.c::add_one_tree: handle NULL from lookup_tree
mark_blob/tree_uninteresting: check for NULL
get_sha1_oneline: check return value of parse_object
read_object_with_reference: don't read beyond the buffer
A failure in prepare_revision_walk can be caused by
a not parseable object.
Signed-off-by: Martin Koegler <mkoegler@auto.tuwien.ac.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since git-upload-pack has to spawn git-pack-objects, it has to make sure
that the latter can be found in the PATH. Without this patch an attempt
to clone or pull via ssh from a server fails if the git tools are not in
the standard PATH on the server even though git clone or git pull were
invoked with --upload-pack=/path/to/git-upload-pack.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
upload-pack spawns two processes, rev-list and pack-objects, and carefully
monitors their status so that it can report failure to the remote end.
This change removes the complicated procedures on the grounds of the
following observations:
- If everything is OK, rev-list closes its output pipe end, upon which
pack-objects (which reads from the pipe) sees EOF and terminates itself,
closing its output (and error) pipes. upload-pack reads from both until
it sees EOF in both. It collects the exit codes of the child processes
(which indicate success) and terminates successfully.
- If rev-list sees an error, it closes its output and terminates with
failure. pack-objects sees EOF in its input and terminates successfully.
Again upload-pack reads its inputs until EOF. When it now collects
the exit codes of its child processes, it notices the failure of rev-list
and signals failure to the remote end.
- If pack-objects sees an error, it terminates with failure. Since this
breaks the pipe to rev-list, rev-list is killed with SIGPIPE.
upload-pack reads its input until EOF, then collects the exit codes of
the child processes, notices their failures, and signals failure to the
remote end.
- If upload-pack itself dies unexpectedly, pack-objects is killed with
SIGPIPE, and subsequently also rev-list.
The upshot of this is that precise monitoring of child processes is not
required because both terminate if either one of them dies unexpectedly.
This allows us to use finish_command() and finish_async() instead of
an explicit waitpid(2) call.
The change is smaller than it looks because most of it only reduces the
indentation of a large part of the inner loop.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This gets rid of an explicit fork().
Since upload-pack has to coordinate two processes (rev-list and
pack-objects), we cannot use the normal finish_async(), but have to monitor
the process explicitly. Hence, there are no changes at this front.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
This allows us later to use start_async() with this function, and at
the same time is a nice cleanup that makes a long function
(create_pack_file()) shorter.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
This gets rid of an explicit fork/exec.
Since upload-pack has to coordinate two processes (rev-list and
pack-objects), we cannot use the normal finish_command(), but have to
monitor the processes explicitly. Hence, the waitpid() call remains.
Signed-off-by: Johannes Sixt <johannes.sixt@telecom.at>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
This uses "git-apply --whitespace=strip" to fix whitespace errors that have
crept in to our source files over time. There are a few files that need
to have trailing whitespaces (most notably, test vectors). The results
still passes the test, and build result in Documentation/ area is unchanged.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Right now, we don't close the read end of the pipe when git-upload-pack
runs git-pack-object, so we hang forever (why don't we get SIGALRM?)
instead of dying with SIGPIPE if the latter dies, which seems to be the
norm if the client disconnects.
Thanks to Johannes Schindelin <Johannes.Schindelin@gmx.de> for
pointing out where this close() needed to go.
This patch has been tested on kernel.org for several weeks and appear
to resolve the problem of git-upload-pack processes hanging around
forever.
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
* 'js/fetch-progress' (early part):
Fixup no-progress for fetch & clone
fetch & clone: do not output progress when not on a tty
Conflicts:
git-fetch.sh
The intent of the commit 'fetch & clone: do not output progress when
not on a tty' was to make fetching and cloning less chatty when
output was not redirected (such as in a cron job).
However, there was a serious thinko in that commit. It assumed that
the client _and_ the server got this update at the same time. But
this is obviously not the case, and therefore upload-pack died on
seeing the option "--no-progress".
This patch fixes that issue by making it a protocol option. So, until
your server is updated, you still see the progress, but once the
server has this patch, it will be quiet.
A minor issue was also fixed: when cloning, the checkout did not
heed no_progress.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Previous step converted use of strncmp() with literal string
mechanically even when the result is only used as a boolean:
if (!strncmp("foo", arg, 3)) ==> if (!(-prefixcmp(arg, "foo")))
This step manually cleans them up to read:
if (!prefixcmp(arg, "foo"))
Signed-off-by: Junio C Hamano <junkio@cox.net>
This mechanically converts strncmp() to use prefixcmp(), but only when
the parameters match specific patterns, so that they can be verified
easily. Leftover from this will be fixed in a separate step, including
idiotic conversions like
if (!strncmp("foo", arg, 3))
=>
if (!(-prefixcmp(arg, "foo")))
This was done by using this script in px.perl
#!/usr/bin/perl -i.bak -p
if (/strncmp\(([^,]+), "([^\\"]*)", (\d+)\)/ && (length($2) == $3)) {
s|strncmp\(([^,]+), "([^\\"]*)", (\d+)\)|prefixcmp($1, "$2")|;
}
if (/strncmp\("([^\\"]*)", ([^,]+), (\d+)\)/ && (length($1) == $3)) {
s|strncmp\("([^\\"]*)", ([^,]+), (\d+)\)|(-prefixcmp($2, "$1"))|;
}
and running:
$ git grep -l strncmp -- '*.c' | xargs perl px.perl
Signed-off-by: Junio C Hamano <junkio@cox.net>
This adds the option "--no-progress" to fetch-pack and upload-pack,
and makes fetch and clone pass this option when stdout is not a tty.
While at documenting that option, also document --strict and --timeout
options for upload-pack.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
We currently do not support fetching/cloning from a shallow repository
nor pushing into one. Make sure these are not attempted so that we
do not have to worry about corrupting repositories needlessly.
Signed-off-by: Junio C Hamano <junkio@cox.net>
We have a number of badly checked write() calls. Often we are
expecting write() to write exactly the size we requested or fail,
this fails to handle interrupts or short writes. Switch to using
the new write_in_full(). Otherwise we at a minimum need to check
for EINTR and EAGAIN, where this is appropriate use xwrite().
Note, the changes to config handling are much larger and handled
in the next patch in the sequence.
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
We have a number of badly checked read() calls. Often we are
expecting read() to read exactly the size we requested or fail, this
fails to handle interrupts or short reads. Add a read_in_full()
providing those semantics. Otherwise we at a minimum need to check
for EINTR and EAGAIN, where this is appropriate use xread().
Signed-off-by: Andy Whitcroft <apw@shadowen.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This is to adjust to:
count-objects -v: show number of packs as well.
which will break a test in this series.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This is a mechanical clean-up of the way *.c files include
system header files.
(1) sources under compat/, platform sha-1 implementations, and
xdelta code are exempt from the following rules;
(2) the first #include must be "git-compat-util.h" or one of
our own header file that includes it first (e.g. config.h,
builtin.h, pkt-line.h);
(3) system headers that are included in "git-compat-util.h"
need not be included in individual C source files.
(4) "git-compat-util.h" does not have to include subsystem
specific header files (e.g. expat.h).
Signed-off-by: Junio C Hamano <junkio@cox.net>
A commit may have been put on the shallow list, and then reached from
another branch and marked NOT_SHALLOW without being removed from the
list.
Signed-off-by: Alexandre Julliard <julliard@winehq.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Now, by saying "git fetch -depth <n> <repo>" you can deepen
a shallow repository.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
By specifying a depth, you can now clone a repository such that
all fetched ancestor-chains' length is at most "depth". For example,
if the upstream repository has only 2 branches ("A" and "B"), which
are linear, and you specify depth 3, you will get A, A~1, A~2, A~3,
B, B~1, B~2, and B~3. The ends are automatically made shallow
commits.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
A shallow commit is a commit which has parents, which in turn are
"grafted away", i.e. the commit appears as if it were a root.
Since these shallow commits should not be edited by the user, but
only by core git, they are recorded in the file $GIT_DIR/shallow.
A repository containing shallow commits is called shallow.
The advantage of a shallow repository is that even if the upstream
contains lots of history, your local (shallow) repository needs not
occupy much disk space.
The disadvantage is that you might miss a merge base when pulling
some remote branch.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
It is trivial to do now, and it is needed for the upcoming shallow
clone stuff.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
* lj/refs: (63 commits)
Fix show-ref usagestring
t3200: git-branch testsuite update
sha1_name.c: avoid compilation warnings.
Make git-branch a builtin
ref-log: fix D/F conflict coming from deleted refs.
git-revert with conflicts to behave as git-merge with conflicts
core.logallrefupdates thinko-fix
git-pack-refs --all
core.logallrefupdates create new log file only for branch heads.
Remove bashism from t3210-pack-refs.sh
ref-log: allow ref@{count} syntax.
pack-refs: call fflush before fsync.
pack-refs: use lockfile as everybody else does.
git-fetch: do not look into $GIT_DIR/refs to see if a tag exists.
lock_ref_sha1_basic does not remove empty directories on BSD
Do not create tag leading directories since git update-ref does it.
Check that a tag exists using show-ref instead of looking for the ref file.
Use git-update-ref to delete a tag instead of rm()ing the ref file.
Fix refs.c;:repack_without_ref() clean-up path
Clean up "git-branch.sh" and add remove recursive dir test cases.
...
There is no reason not to always do this when both ends agree.
Therefore a client that can accept offsets to delta base always sends
the "ofs-delta" flag. The server will stream a pack with or without
offset to delta base depending on whether that flag is provided or not
with no additional cost.
Signed-off-by: Nicolas Pitre <nico@cam.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This adds a "int *flag" parameter to resolve_ref() and makes
for_each_ref() family to call callback function with an extra
"int flag" parameter. They are used to give two bits of
information (REF_ISSYMREF and REF_ISPACKED) about the ref.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This is a long overdue fix to the API for for_each_ref() family
of functions. It allows the callers to specify a callback data
pointer, so that the caller does not have to use static
variables to communicate with the callback funciton.
The updated for_each_ref() family takes a function of type
int (*fn)(const char *, const unsigned char *, void *)
and a void pointer as parameters, and calls the function with
the name of the ref and its SHA-1 with the caller-supplied void
pointer as parameters.
The commit updates two callers, builtin-name-rev.c and
builtin-pack-refs.c as an example.
Signed-off-by: Junio C Hamano <junkio@cox.net>
The original side-band support added to the upload-pack protocol used the
default 1000-byte packet length. The pkt-line format allows up to 64k, so
prepare the receiver for the maximum size, and have the uploader and
downloader negotiate if larger packet length is allowed.
Signed-off-by: Junio C Hamano <junkio@cox.net>
The server side support; this is just the very low level, and the
caller needs to know which band it wants to send things out.
Signed-off-by: Junio C Hamano <junkio@cox.net>
(cherry picked from b786552b67878c7780c50def4c069d46dc54efbe commit)
This abstracts away the size of the hash values when copying them
from memory location to memory location, much as the introduction
of hashcmp abstracted away hash value comparsion.
A few call sites were using char* rather than unsigned char* so
I added the cast rather than open hashcpy to be void*. This is a
reasonable tradeoff as most call sites already use unsigned char*
and the existing hashcmp is also declared to be unsigned char*.
[jc: Splitted the patch to "master" part, to be followed by a
patch for merge-recursive.c which is not in "master" yet.
Fixed the cast in the latter hunk to combine-diff.c which was
wrong in the original.
Also converted ones left-over in combine-diff.c, diff-lib.c and
upload-pack.c ]
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
[jc: I needed to hand merge the changes to the updated codebase,
so the result needs to be checked.]
Signed-off-by: David Rientjes <rientjes@google.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
When the downloader has more roots than we do, we will see many
"have" that leads to the root we do not have and let the other
side walk all the way to that root. Tell them to stop sending the
branch'es ancestors by sending a fake "ACK" when we already have
common ancestor for the wanted refs.
Signed-off-by: Junio C Hamano <junkio@cox.net>
No changes to what it does, but separating the codepath clearly
with if ... else if ... chain makes it easier to follow.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This updates the type-enumeration constants introduced to reduce
the memory footprint of "struct object" to match the type bits
already used in the packfile format, by removing the former
(i.e. TYPE_* constant macros) and using the latter (i.e. enum
object_type) throughout the code for consistency.
Eventually we can stop passing around the "type strings"
entirely, and this will help - no confusion about two different
integer enumeration.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
By using object_array data structure, lift the old limitation of
MAX_HAS/MAX_NEEDS. While we are at it, rename the variables
that hold the objects we use to compute common ancestor to match
the message used at the protocol level. What the other end has
and we also do are "have"s, and what the other end asks for are
"want"s.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Merlyn reports that <sys/poll.h> on OpenBSD 3.8 includes <ctype.h>
and having our custom ctype (done in git-compat-util.h which is
included via cache.h) makes upload-pack.c uncompilable. Try to
work it around by including the system headers first.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This implements a protocol extension between fetch-pack and
upload-pack to allow stderr stream from upload-pack (primarily
used for the progress bar display) to be passed back.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This does not implement sideband for propagating the status to
the downloader yet, but add code to capture the standard error
output from the pack-objects process in preparation for sending
it off to the client when the protocol extension allows us to do
so.
Signed-off-by: Junio C Hamano <junkio@cox.net>
When the repository on the remote side is corrupted, rev-list
spawned from upload-pack would die with error, but pack-objects
that reads from the rev-list happily created a packfile that can
be unpacked by the downloader. When this happens, the resulting
packfile is not corrupted and unpacks cleanly, but the list of
the objects contained in it is not what the protocol exchange
computed.
This update makes upload-pack to monitor its subprocesses, and
when either of them dies with error, sends an incomplete pack
data to the downloader to cause it to fail.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This shrinks "struct object" by a small amount, by getting rid of the
"struct type *" pointer and replacing it with a 3-bit bitfield instead.
In addition, we merge the bitfields and the "flags" field, which
incidentally should also remove a useless 4-byte padding from the object
when in 64-bit mode.
Now, our "struct object" is still too damn large, but it's now less
obviously bloated, and of the remaining fields, only the "util" (which is
not used by most things) is clearly something that should be eventually
discarded.
This shrinks the "git-rev-list --all" memory use by about 2.5% on the
kernel archive (and, perhaps more importantly, on the larger mozilla
archive). That may not sound like much, but I suspect it's more on a
64-bit platform.
There are other remaining inefficiencies (the parent lists, for example,
probably have horrible malloc overhead), but this was pretty obvious.
Most of the patch is just changing the comparison of the "type" pointer
from one of the constant string pointers to the appropriate new TYPE_xxx
small integer constant.
Signed-off-by: Linus Torvalds <torvalds@osdl.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Mark Wooding noticed there was a type mismatch warning in git.c; this
patch does things slightly differently (mostly tightening const) and
was what I was holding onto, waiting for the setup-revisions change
to be merged into the master branch.
Signed-off-by: Junio C Hamano <junkio@cox.net>
* jc/rev-list:
rev-list --objects: use full pathname to help hashing.
rev-list --objects-edge: remove duplicated edge commit output.
rev-list --objects-edge
* jc/pack-thin:
pack-objects: hash basename and direname a bit differently.
pack-objects: allow "thin" packs to exceed depth limits
pack-objects: use full pathname to help hashing with "thin" pack.
pack-objects: thin pack micro-optimization.
Use thin pack transfer in "git fetch".
Add git-push --thin.
send-pack --thin: use "thin pack" delta transfer.
Thin pack - create packfile with missing delta base.
Conflicts:
pack-objects.c (taking "next")
send-pack.c (taking "next")
The git suite may not be in PATH (and thus programs such as
git-send-pack could not exec git-rev-list). Thus there is a need for
logic that will locate these programs. Modifying PATH is not
desirable as it result in behavior differing from the user's
intentions, as we may end up prepending "/usr/bin" to PATH.
- git C programs will use exec*_git_cmd() APIs to exec sub-commands.
- exec*_git_cmd() will execute a git program by searching for it in
the following directories:
1. --exec-path (as used by "git")
2. The GIT_EXEC_PATH environment variable.
3. $(gitexecdir) as set in Makefile (default value $(bindir)).
- git wrapper will modify PATH as before to enable shell scripts to
invoke "git-foo" commands.
Ideally, shell scripts should use the git wrapper to become independent
of PATH, and then modifying PATH will not be necessary.
[jc: with minor updates after a brief review.]
Signed-off-by: Michal Ostrowski <mostrows@watson.ibm.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch basically just removes the redundant code from
{receive,upload}-pack.c in favour of the library code in path.c.
Signed-off-by: Andreas Ericsson <ae@op5.se>
Signed-off-by: Junio C Hamano <junkio@cox.net>
One caller of deref_tag() was not careful enough to make sure
what deref_tag() returned was not NULL (i.e. we found a tag
object that points at an object we do not have). Fix it, and
warn about refs that point at such an incomplete tag where
needed.
Signed-off-by: Junio C Hamano <junkio@cox.net>
This implements three things (trying very hard to be backwards
compatible):
It sends the "multi_ack" capability via the mechanism proposed by
Sergey Vlasov.
When the client sends "multi_ack" with at least one "want", multi_ack
is enabled.
When multi_ack is enabled, "continue" is appended to each "ACK" until
either the server can not store more refs, or "done" is received.
In contrast to the original protocol, as long as "continue" is sent,
flushes are answered by a "NAK" (not just until an "ACK" was sent),
and if "continue" was sent at least once, the last message is an
"ACK" without "continue".
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch is based on Junio's proposal. It marks parents of common revs
so that they do not clutter up the has_sha1 array.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
upload-pack would set create_full_pack=1 if nr_has==0, but would ask later
if nr_needs<MAX_NEEDS. If that proves true, it would ignore create_full_pack,
and arguments would be written into unreserved memory.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This makes sure what the other end asks for are among what we
offered to give them. Otherwise we would end up running
git-rev-list with 20-byte nonsense, only to find it either die
(because the object was not found) or waste time (because we
ended up serving that phony 'client').
Also avoid wasting needs_sha1 pool to record duplicates, and
detect cloning requests better.
[this used to be on top of Johannes fetch-pack enhancements,
which we are rewinding it for further testing for now, so
the commit is rebased.]
Signed-off-by: Junio C Hamano <junkio@cox.net>
The current fetch/upload protocol works like this:
- client sends revs it wants to have via "want" messages
- client sends a flush message (message with len 0)
- client sends revs it has via "have" messages
- after one window (32 revs), a flush is sent
- after each subsequent window, a flush is sent, and an ACK/NAK is received.
(NAK means that server does not have any of the transmitted revs;
ACK sends also the sha1 of the rev server has)
- when the first ACK is received, client sends "done", and does not expect
any further messages
One special case, though:
- if no ACK is received (only NAK's), and client runs out of revs to send,
"done" is sent, and server sends just one more "NAK"
A smarter scheme, which actually has a chance to detect more than one
common rev, would be to send more than just one ACK. This patch implements
the server side of the following extension to the protocol:
- client sends at least one "want" message with "multi_ack" appended, like
"want 1234567890123456789012345678901234567890 multi_ack"
- if the server understands that extension, it will send ACK messages for all
revs it has, not just the first one
- server appends "continue" to the ACK messages like
"ACK 1234567890123456789012345678901234567890 continue"
until it has MAX_HAS-1 revs. In this manner, client knows when to
stop sending revs by checking for the substring "continue" (and
further knows that server understands multi_ack)
In this manner, the protocol stays backwards compatible, since both client
must send "want ... multi_ack" and server must answer with "ACK ...
continue" to enable the extension.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This patch is based on Junio's proposal. It marks parents of common revs
so that they do not clutter up the has_sha1 array.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
Later round would further improve fetch-pack not to send useless "have",
but in the meantime, increase it to help upload-pack to find more common
commits, as discussed on the list.
Signed-off-by: Junio C Hamano <junkio@cox.net>
It turns out that not only did git-daemon do DWIM, but git-upload-pack
does as well. This is bad; security checks have to be performed *after*
canonicalization, not before.
Additionally, the current git-daemon can be trivially DoSed by spewing
SYNs at the target port.
This patch adds a --strict option to git-upload-pack to disable all
DWIM, a --timeout option to git-daemon and git-upload-pack, and an
--init-timeout option to git-daemon (which is typically set to a much
lower value, since the initial request should come immediately from the
client.)
Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>
This updates git-ls-remote to show SHA1 names of objects that are
referred by tags, in the "ref^{}" notation.
This would make git-findtags (without -t flag) almost trivial.
git-peek-remote . |
sed -ne "s:^$target "'refs/tags/\(.*\)^{}$:\1:p'
Also Pasky could do:
git-ls-remote --tags $remote |
sed -ne 's:\( refs/tags/.*\)^{}$:\1:p'
to find out what object each of the remote tags refers to, and
if he has one locally, run "git-fetch $remote tag $tagname" to
automatically catch up with the upstream tags.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Cloning from a repository with more than 256 refs (heads and tags
included) will choke, because upload-pack has a built-in limit of
feeding not more than MAX_NEEDS (currently 256) heads to underlying
git-rev-list. This is a problem when cloning a repository with many
tags, like http://www.linux-mips.org/pub/scm/linux.git, which has 290+
tags.
This commit introduces a new flag, --all, to git-rev-list, to include
all refs in the repository. Updated upload-pack detects requests that
ask more than MAX_NEEDS refs, and sends everything back instead.
We may probably want to tweak the definitions of MAX_NEEDS and
MAX_HAS, but that is a separate topic.
Signed-off-by: Junio C Hamano <junkio@cox.net>
Solaris 8 doesn't have the newer unsetenv() and setenv()
functions, so replace them with putenv(). The one use of
unsetenv() in fsck-cache.c now sets GIT_ALTERNATE_OBJECT_
DIRECTORIES to the empty string. Every place that var
is used, NULLs are also replaced with empty strings, so
it's ok.
Signed-off-by: Jason Riedy <ejr@cs.berkeley.edu>
Now that git-clone-pack exists, we actually have somebody requesting
more than just a single head in a pack. So allow the Jeff's of this
world to clone things with tens of heads.
"git_path()" returns a static pathname pointer into the git directory
using a printf-like format specifier.
"head_ref()" works like "for_each_ref()", except for just the HEAD.
It returns the result SHA1 on stdout, so you can do
remote=$(git-fetch-pack host:dir branchname)
and it will unpack the objects and "remote" will be the SHA1 name of the
branch on the other side. You can then save that off, or merge it, or
whatever.
It's meant to be used by "git fetch" for the local and ssh case.
It doesn't actually do the fetching now, but it does discover the common
commit point.
