Commit Graph

1207 Commits

Author SHA1 Message Date
Junio C Hamano
10b944b37b Merge branch 'jk/alloc-commit-id'
Make sure all in-core commit objects are assigned a unique number
so that they can be annotated using the commit-slab API.

* jk/alloc-commit-id:
  diff-tree: avoid lookup_unknown_object
  object_as_type: set commit index
  alloc: factor out commit index
  add object_as_type helper for casting objects
  parse_object_buffer: do not set object type
  move setting of object->type to alloc_* functions
  alloc: write out allocator definitions
  alloc.c: remove the alloc_raw_commit_node() function
2014-07-22 10:59:25 -07:00
Junio C Hamano
9f2de9c121 Merge branch 'kb/perf-trace'
* kb/perf-trace:
  api-trace.txt: add trace API documentation
  progress: simplify performance measurement by using getnanotime()
  wt-status: simplify performance measurement by using getnanotime()
  git: add performance tracing for git's main() function to debug scripts
  trace: add trace_performance facility to debug performance issues
  trace: add high resolution timer function to debug performance issues
  trace: add 'file:line' to all trace output
  trace: move code around, in preparation to file:line output
  trace: add current timestamp to all trace output
  trace: disable additional trace output for unit tests
  trace: add infrastructure to augment trace output with additional info
  sha1_file: change GIT_TRACE_PACK_ACCESS logging to use trace API
  Documentation/git.txt: improve documentation of 'GIT_TRACE*' variables
  trace: improve trace performance
  trace: remove redundant printf format attribute
  trace: consistently name the format parameter
  trace: move trace declarations from cache.h to new trace.h
2014-07-22 10:59:19 -07:00
Junio C Hamano
19a249ba83 Merge branch 'rs/ref-transaction-0'
Early part of the "ref transaction" topic.

* rs/ref-transaction-0:
  refs.c: change ref_transaction_update() to do error checking and return status
  refs.c: remove the onerr argument to ref_transaction_commit
  update-ref: use err argument to get error from ref_transaction_commit
  refs.c: make update_ref_write update a strbuf on failure
  refs.c: make ref_update_reject_duplicates take a strbuf argument for errors
  refs.c: log_ref_write should try to return meaningful errno
  refs.c: make resolve_ref_unsafe set errno to something meaningful on error
  refs.c: commit_packed_refs to return a meaningful errno on failure
  refs.c: make remove_empty_directories always set errno to something sane
  refs.c: verify_lock should set errno to something meaningful
  refs.c: make sure log_ref_setup returns a meaningful errno
  refs.c: add an err argument to repack_without_refs
  lockfile.c: make lock_file return a meaningful errno on failurei
  lockfile.c: add a new public function unable_to_lock_message
  refs.c: add a strbuf argument to ref_transaction_commit for error logging
  refs.c: allow passing NULL to ref_transaction_free
  refs.c: constify the sha arguments for ref_transaction_create|delete|update
  refs.c: ref_transaction_commit should not free the transaction
  refs.c: remove ref_transaction_rollback
2014-07-21 11:18:37 -07:00
Junio C Hamano
c9831bb09d Merge branch 'kb/path-max-must-go'
* kb/path-max-must-go:
  cache.h: rename cache_def_free to cache_def_clear
2014-07-16 11:32:33 -07:00
Junio C Hamano
788cef81d4 Merge branch 'nd/split-index'
An experiment to use two files (the base file and incremental
changes relative to it) to represent the index to reduce I/O cost
of rewriting a large index when only small part of the working tree
changes.

* nd/split-index: (32 commits)
  t1700: new tests for split-index mode
  t2104: make sure split index mode is off for the version test
  read-cache: force split index mode with GIT_TEST_SPLIT_INDEX
  read-tree: note about dropping split-index mode or index version
  read-tree: force split-index mode off on --index-output
  rev-parse: add --shared-index-path to get shared index path
  update-index --split-index: do not split if $GIT_DIR is read only
  update-index: new options to enable/disable split index mode
  split-index: strip pathname of on-disk replaced entries
  split-index: do not invalidate cache-tree at read time
  split-index: the reading part
  split-index: the writing part
  read-cache: mark updated entries for split index
  read-cache: save deleted entries in split index
  read-cache: mark new entries for split index
  read-cache: split-index mode
  read-cache: save index SHA-1 after reading
  entry.c: update cache_changed if refresh_cache is set in checkout_entry()
  cache-tree: mark istate->cache_changed on prime_cache_tree()
  cache-tree: mark istate->cache_changed on cache tree update
  ...
2014-07-16 11:25:40 -07:00
Ronnie Sahlberg
76d70dc0c6 refs.c: make resolve_ref_unsafe set errno to something meaningful on error
Making errno when returning from resolve_ref_unsafe() meaningful,
which should fix

 * a bug in lock_ref_sha1_basic, where it assumes EISDIR
   means it failed due to a directory being in the way

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Michael Haggerty <mhagger@alum.mit.edu>
2014-07-14 11:54:42 -07:00
Ronnie Sahlberg
6af926e8bc lockfile.c: add a new public function unable_to_lock_message
Introducing a new unable_to_lock_message helper, which has nicer
semantics than unable_to_lock_error and cleans up lockfile.c a little.

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Acked-by: Michael Haggerty <mhagger@alum.mit.edu>
2014-07-14 11:54:40 -07:00
Jeff King
94d5a22cf6 alloc: factor out commit index
We keep a static counter to set the commit index on newly
allocated objects. However, since we also need to set the
index on any_objects which are converted to commits, let's
make the counter available as a public function.

While we're moving it, let's make sure the counter is
allocated as an unsigned integer to match the index field in
"struct commit".

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-13 18:59:05 -07:00
Karsten Blees
2a60839150 cache.h: rename cache_def_free to cache_def_clear
Rename cache_def_free to cache_def_clear as it doesn't free the struct
cache_def, but just clears its content.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-13 10:12:37 -07:00
Junio C Hamano
11def366e5 Merge branch 'kb/path-max-must-go'
* kb/path-max-must-go:
  symlinks: remove PATH_MAX limitation
2014-07-10 11:27:47 -07:00
Karsten Blees
e7c7305300 symlinks: remove PATH_MAX limitation
'git checkout' fails if a directory is longer than PATH_MAX, because the
lstat_cache in symlinks.c checks if the leading directory exists using
PATH_MAX-bounded string operations.

Remove the limitation by using strbuf instead.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-07 11:22:42 -07:00
Junio C Hamano
1881d2b88c Merge branch 'ym/fix-opportunistic-index-update-race' into maint
"git status", even though it is a read-only operation, tries to
update the index with refreshed lstat(2) info to optimize future
accesses to the working tree opportunistically, but this could
race with a "read-write" operation that modify the index while it
is running.  Detect such a race and avoid overwriting the index.

* ym/fix-opportunistic-index-update-race:
  read-cache.c: verify index file before we opportunistically update it
  wrapper.c: add xpread() similar to xread()
2014-06-25 11:49:48 -07:00
Jeremiah Mahler
ccdd4a0f3c cleanup duplicate name_compare() functions
We often represent our strings as a counted string, i.e. a pair of
the pointer to the beginning of the string and its length, and the
string may not be NUL terminated to that length.

To compare a pair of such counted strings, unpack-trees.c and
read-cache.c implement their own name_compare() functions
identically.  In addition, the cache_name_compare() function in
read-cache.c is nearly identical.  The only difference is when one
string is the prefix of the other string, in which case
name_compare() returns -1/+1 to show which one is longer, and
cache_name_compare() returns the difference of the lengths to show
the same information.

Unify these three functions by using the implementation from
cache_name_compare().  This does not make any difference to the
existing and future callers, as they must be paying attention only
to the sign of the returned value (and not the magnitude) because
the original implementations of these two functions return values
returned by memcmp(3) when the one string is not a prefix of the
other string, and the only thing memcmp(3) guarantees its callers is
the sign of the returned value, not the magnitude.

Signed-off-by: Jeremiah Mahler <jmmahler@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-20 10:12:14 -07:00
Karsten Blees
5991a55c54 trace: move trace declarations from cache.h to new trace.h
Also include direct dependencies (strbuf.h and git-compat-util.h for
__attribute__) so that trace.h can be used independently of cache.h, e.g.
in test programs.

Signed-off-by: Karsten Blees <blees@dcon.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-17 09:37:47 -07:00
Junio C Hamano
b83163643b Merge branch 'sk/windows-unc-path'
* sk/windows-unc-path:
  Windows: allow using UNC path for git repository
2014-06-16 10:07:03 -07:00
Nguyễn Thái Ngọc Duy
3e52f70b15 t1700: new tests for split-index mode
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:42 -07:00
Nguyễn Thái Ngọc Duy
c18b80a0e8 update-index: new options to enable/disable split index mode
If you have a large work tree but only make changes in a subset, then
$GIT_DIR/index's size should be stable after a while. If you change
branches that touch something else, $GIT_DIR/index's size may grow
large that it becomes as slow as the unified index. Do --split-index
again occasionally to force all changes back to the shared index and
keep $GIT_DIR/index small.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:41 -07:00
Nguyễn Thái Ngọc Duy
b3c96fb158 split-index: strip pathname of on-disk replaced entries
We know the positions of replaced entries via the replace bitmap in
"link" extension, so the "name" path does not have to be stored (it's
still in the shared index). With this, we also have a way to
distinguish additions vs replacements at load time and can catch
broken "link" extensions.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:41 -07:00
Nguyễn Thái Ngọc Duy
ce7c614bce split-index: do not invalidate cache-tree at read time
We are sure that after merge_base_index() is done. cache-tree can
still be used with the final index. So don't destroy cache tree.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:41 -07:00
Nguyễn Thái Ngọc Duy
078a58e825 read-cache: mark updated entries for split index
The large part of this patch just follows CE_ENTRY_CHANGED
marks. replace_index_entry() is updated to update
split_index->base->cache[] as well so base->cache[] does not reference
to a freed entry.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:40 -07:00
Nguyễn Thái Ngọc Duy
5fc2fc8fa2 read-cache: split-index mode
This split-index mode is designed to keep write cost proportional to
the number of changes the user has made, not the size of the work
tree. (Read cost is another matter, to be dealt separately.)

This mode stores index info in a pair of $GIT_DIR/index and
$GIT_DIR/sharedindex.<SHA-1>. sharedindex is large and unchanged over
time while "index" is smaller and updated often. Format details are in
index-format.txt, although not everything is implemented in this
patch.

Shared indexes are not automatically removed, because it's unclear if
the shared index is needed by any (even temporary) indexes by just
looking at it. After a while you'll collect stale shared indexes. The
good news is one shared index is useable for long, until
$GIT_DIR/index becomes too big and sluggish that the new shared index
must be created.

The safest way to clean shared indexes is to turn off split index
mode, so shared files are all garbage, delete them all, then turn on
split index mode again.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:39 -07:00
Nguyễn Thái Ngọc Duy
e93021b20a read-cache: save index SHA-1 after reading
Also update SHA-1 after writing. If we do not do that, the second
read_index() will see "initialized" variable already set and not read
.git/index again, which is fine, except istate->sha1 now has a stale
value.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:39 -07:00
Nguyễn Thái Ngọc Duy
d4a2024aef entry.c: update cache_changed if refresh_cache is set in checkout_entry()
Other fill_stat_cache_info() is on new entries, which should set
CE_ENTRY_ADDED in cache_changed, so we're safe.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:39 -07:00
Nguyễn Thái Ngọc Duy
a5400efe29 cache-tree: mark istate->cache_changed on cache tree invalidation
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:39 -07:00
Nguyễn Thái Ngọc Duy
6c306a34ee resolve-undo: be specific what part of the index has changed
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:38 -07:00
Nguyễn Thái Ngọc Duy
e636a7b4d0 read-cache: be specific what part of the index has changed
cache entry additions, removals and modifications are separated
out. The rest of changes are still in the catch-all flag
SOMETHING_CHANGED, which would be more specific later.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:38 -07:00
Nguyễn Thái Ngọc Duy
ce51bf09f8 read-cache: store in-memory flags in the first 12 bits of ce_flags
We're running out of room for in-memory flags. But since b60e188
(Strip namelen out of ce_flags into a ce_namelen field - 2012-07-11),
we copy the namelen (first 12 bits) to ce_namelen field. So those bits
are free to use. Just make sure we do not accidentally write any
in-memory flags back.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:38 -07:00
Nguyễn Thái Ngọc Duy
626f35c893 read-cache: relocate and unexport commit_locked_index()
This function is now only used by write_locked_index(). Move it to
read-cache.c (because read-cache.c will need to be aware of
alternate_index_output later) and unexport it.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:38 -07:00
Nguyễn Thái Ngọc Duy
03b8664772 read-cache: new API write_locked_index instead of write_index/write_cache
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-13 11:49:10 -07:00
Cezary Zawadka
c2369bdf7f Windows: allow using UNC path for git repository
[efl: moved MinGW-specific part to compat/]
[jes: fixed compilation on non-Windows]

Eric Sunshine fixed mingw_offset_1st_component() to return
consistently "foo" for UNC "//machine/share/foo", cf

http://groups.google.com/group/msysgit/browse_thread/thread/c0af578549b5dda0

Author: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Cezary Zawadka <czawadka@gmail.com>
Signed-off-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Erik Faye-Lund <kusmabite@gmail.com>
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Stepan Kasal <kasal@ucw.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-10 13:30:04 -07:00
Junio C Hamano
1e2600dd6a Merge branch 'nd/status-auto-comment-char'
* nd/status-auto-comment-char:
  commit: allow core.commentChar=auto for character auto selection
  config: be strict on core.commentChar
2014-06-06 11:36:10 -07:00
Junio C Hamano
610a14f643 Merge branch 'jk/squelch-compiler-warning-from-funny-error-macro'
* jk/squelch-compiler-warning-from-funny-error-macro:
  let clang use the constant-return error() macro
  inline constant return from error() function
2014-06-06 11:21:36 -07:00
Junio C Hamano
e1857af923 Merge branch 'jk/commit-date-approxidate'
* jk/commit-date-approxidate:
  commit: accept more date formats for "--date"
  commit: print "Date" line when the user has set date
  pretty: make show_ident_date public
  commit: use split_ident_line to compare author/committer
2014-06-03 12:06:46 -07:00
Junio C Hamano
9af098c29b Merge branch 'ym/fix-opportunistic-index-update-race'
Read-only operations such as "git status" that internally refreshes
the index write out the refreshed index to the disk to optimize
future accesses to the working tree, but this could race with a
"read-write" operation that modify the index while it is running.
Detect such a race and avoid overwriting the index.

Duy raised a good point that we may need to do the same for the
normal writeout codepath, not just the "opportunistic" update
codepath.  While that is true, nobody sane would be running two
simultaneous operations that are clearly write-oriented competing
with each other against the same index file.  So in that sense that
can be done as a less urgent follow-up for this topic.

* ym/fix-opportunistic-index-update-race:
  read-cache.c: verify index file before we opportunistically update it
  wrapper.c: add xpread() similar to xread()
2014-06-03 12:06:41 -07:00
Junio C Hamano
8eaf517835 Merge branch 'ks/tree-diff-nway'
Instead of running N pair-wise diff-trees when inspecting a
N-parent merge, find the set of paths that were touched by walking
N+1 trees in parallel.  These set of paths can then be turned into
N pair-wise diff-tree results to be processed through rename
detections and such.  And N=2 case nicely degenerates to the usual
2-way diff-tree, which is very nice.

* ks/tree-diff-nway:
  mingw: activate alloca
  combine-diff: speed it up, by using multiparent diff tree-walker directly
  tree-diff: rework diff_tree() to generate diffs for multiparent cases as well
  Portable alloca for Git
  tree-diff: reuse base str(buf) memory on sub-tree recursion
  tree-diff: no need to call "full" diff_tree_sha1 from show_path()
  tree-diff: rework diff_tree interface to be sha1 based
  tree-diff: diff_tree() should now be static
  tree-diff: remove special-case diff-emitting code for empty-tree cases
  tree-diff: simplify tree_entry_pathcmp
  tree-diff: show_path prototype is not needed anymore
  tree-diff: rename compare_tree_entry -> tree_entry_pathcmp
  tree-diff: move all action-taking code out of compare_tree_entry()
  tree-diff: don't assume compare_tree_entry() returns -1,0,1
  tree-diff: consolidate code for emitting diffs and recursion in one place
  tree-diff: show_tree() is not needed
  tree-diff: no need to pass match to skip_uninteresting()
  tree-diff: no need to manually verify that there is no mode change for a path
  combine-diff: move changed-paths scanning logic into its own function
  combine-diff: move show_log_first logic/action out of paths scanning
2014-06-03 12:06:40 -07:00
Nguyễn Thái Ngọc Duy
84c9dc2c5a commit: allow core.commentChar=auto for character auto selection
When core.commentChar is "auto", the comment char starts with '#' as
in default but if it's already in the prepared message, find another
char in a small subset. This should stop surprises because git strips
some lines unexpectedly.

Note that git is not smart enough to recognize '#' as the comment char
in custom templates and convert it if the final comment char is
different. It thinks '#' lines in custom templates as part of the
commit message. So don't use this with custom templates.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-05-19 13:37:25 -07:00
Jeff King
ff0a80af72 let clang use the constant-return error() macro
Commit e208f9c converted error() into a macro to make its
constant return value more apparent to calling code.  Commit
5ded807 prevents us using this macro with clang, since
clang's -Wunused-value is smart enough to realize that the
constant "-1" is useless in some contexts.

However, since the last commit puts the constant behind an
inline function call, this is enough to prevent the
-Wunused-value warning on both modern gcc and clang. So we
can now re-enable the macro when compiling with clang.

Tested with clang 3.3, 3.4, and 3.5.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-05-06 15:30:40 -07:00
Jeff King
87fe5df365 inline constant return from error() function
Commit e208f9c introduced a macro to turn error() calls
into:

  (error(), -1)

to make the constant return value more visible to the
calling code (and thus let the compiler make better
decisions about the code).

This works well for code like:

  return error(...);

but the "-1" is superfluous in code that just calls error()
without caring about the return value. In older versions of
gcc, that was fine, but gcc 4.9 complains with -Wunused-value.

We can work around this by encapsulating the constant return
value in a static inline function, as gcc specifically
avoids complaining about unused function returns unless the
function has been specifically marked with the
warn_unused_result attribute.

We also use the same trick for config_error_nonbool and
opterror, which learned the same error technique in a469a10.

Reported-by: Felipe Contreras <felipe.contreras@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-05-06 15:30:38 -07:00
Jeff King
d105324655 pretty: make show_ident_date public
We use this function internally to format "Date" lines in
commit logs, but other parts of the code will want it, too.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-05-02 14:13:00 -07:00
Yiannis Marangos
426ddeead6 read-cache.c: verify index file before we opportunistically update it
Before we proceed to opportunistically update the index (often done
by an otherwise read-only operation like "git status" and "git diff"
that internally refreshes the index), we must verify that the
current index file is the same as the one that we read earlier
before we took the lock on it, in order to avoid a possible race.

In the example below git-status does "opportunistic update" and
git-rebase updates the index, but the race can happen in general.

  1. process A calls git-rebase (or does anything that uses the index)

  2. process A applies 1st commit

  3. process B calls git-status (or does anything that updates the index)

  4. process B reads index

  5. process A applies 2nd commit

  6. process B takes the lock, then overwrites process A's changes.

  7. process A applies 3rd commit

As an end result the 3rd commit will have a revert of the 2nd commit.
When process B takes the lock, it needs to make sure that the index
hasn't changed since step 4.

Signed-off-by: Yiannis Marangos <yiannis.marangos@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-10 12:27:58 -07:00
Kirill Smelkov
72441af7c4 tree-diff: rework diff_tree() to generate diffs for multiparent cases as well
Previously diff_tree(), which is now named ll_diff_tree_sha1(), was
generating diff_filepair(s) for two trees t1 and t2, and that was
usually used for a commit as t1=HEAD~, and t2=HEAD - i.e. to see changes
a commit introduces.

In Git, however, we have fundamentally built flexibility in that a
commit can have many parents - 1 for a plain commit, 2 for a simple merge,
but also more than 2 for merging several heads at once.

For merges there is a so called combine-diff, which shows diff, a merge
introduces by itself, omitting changes done by any parent. That works
through first finding paths, that are different to all parents, and then
showing generalized diff, with separate columns for +/- for each parent.
The code lives in combine-diff.c .

There is an impedance mismatch, however, in that a commit could
generally have any number of parents, and that while diffing trees, we
divide cases for 2-tree diffs and more-than-2-tree diffs. I mean there
is no special casing for multiple parents commits in e.g.
revision-walker .

That impedance mismatch *hurts* *performance* *badly* for generating
combined diffs - in "combine-diff: optimize combine_diff_path
sets intersection" I've already removed some slowness from it, but from
the timings provided there, it could be seen, that combined diffs still
cost more than an order of magnitude more cpu time, compared to diff for
usual commits, and that would only be an optimistic estimate, if we take
into account that for e.g. linux.git there is only one merge for several
dozens of plain commits.

That slowness comes from the fact that currently, while generating
combined diff, a lot of time is spent computing diff(commit,commit^2)
just to only then intersect that huge diff to almost small set of files
from diff(commit,commit^1).

That's because at present, to compute combine-diff, for first finding
paths, that "every parent touches", we use the following combine-diff
property/definition:

D(A,P1...Pn) = D(A,P1) ^ ... ^ D(A,Pn)      (w.r.t. paths)

where

D(A,P1...Pn) is combined diff between commit A, and parents Pi

and

D(A,Pi) is usual two-tree diff Pi..A

So if any of that D(A,Pi) is huge, tracting 1 n-parent combine-diff as n
1-parent diffs and intersecting results will be slow.

And usually, for linux.git and other topic-based workflows, that
D(A,P2) is huge, because, if merge-base of A and P2, is several dozens
of merges (from A, via first parent) below, that D(A,P2) will be diffing
sum of merges from several subsystems to 1 subsystem.

The solution is to avoid computing n 1-parent diffs, and to find
changed-to-all-parents paths via scanning A's and all Pi's trees
simultaneously, at each step comparing their entries, and based on that
comparison, populate paths result, and deduce we could *skip*
*recursing* into subdirectories, if at least for 1 parent, sha1 of that
dir tree is the same as in A. That would save us from doing significant
amount of needless work.

Such approach is very similar to what diff_tree() does, only there we
deal with scanning only 2 trees simultaneously, and for n+1 tree, the
logic is a bit more complex:

D(T,P1...Pn) calculation scheme
-------------------------------

D(T,P1...Pn) = D(T,P1) ^ ... ^ D(T,Pn)	(regarding resulting paths set)

    D(T,Pj)		- diff between T..Pj
    D(T,P1...Pn)	- combined diff from T to parents P1,...,Pn

We start from all trees, which are sorted, and compare their entries in
lock-step:

     T     P1       Pn
     -     -        -
    |t|   |p1|     |pn|
    |-|   |--| ... |--|      imin = argmin(p1...pn)
    | |   |  |     |  |
    |-|   |--|     |--|
    |.|   |. |     |. |
     .     .        .
     .     .        .

at any time there could be 3 cases:

    1)  t < p[imin];
    2)  t > p[imin];
    3)  t = p[imin].

Schematic deduction of what every case means, and what to do, follows:

1)  t < p[imin]  ->  ∀j t ∉ Pj  ->  "+t" ∈ D(T,Pj)  ->  D += "+t";  t↓

2)  t > p[imin]

    2.1) ∃j: pj > p[imin]  ->  "-p[imin]" ∉ D(T,Pj)  ->  D += ø;  ∀ pi=p[imin]  pi↓
    2.2) ∀i  pi = p[imin]  ->  pi ∉ T  ->  "-pi" ∈ D(T,Pi)  ->  D += "-p[imin]";  ∀i pi↓

3)  t = p[imin]

    3.1) ∃j: pj > p[imin]  ->  "+t" ∈ D(T,Pj)  ->  only pi=p[imin] remains to investigate
    3.2) pi = p[imin]  ->  investigate δ(t,pi)
     |
     |
     v

    3.1+3.2) looking at δ(t,pi) ∀i: pi=p[imin] - if all != ø  ->

                      ⎧δ(t,pi)  - if pi=p[imin]
             ->  D += ⎨
                      ⎩"+t"     - if pi>p[imin]

    in any case t↓  ∀ pi=p[imin]  pi↓

~

For comparison, here is how diff_tree() works:

D(A,B) calculation scheme
-------------------------

    A     B
    -     -
   |a|   |b|    a < b   ->  a ∉ B   ->   D(A,B) +=  +a    a↓
   |-|   |-|    a > b   ->  b ∉ A   ->   D(A,B) +=  -b    b↓
   | |   | |    a = b   ->  investigate δ(a,b)            a↓ b↓
   |-|   |-|
   |.|   |.|
    .     .
    .     .

~~~~~~~~

This patch generalizes diff tree-walker to work with arbitrary number of
parents as described above - i.e. now there is a resulting tree t, and
some parents trees tp[i] i=[0..nparent). The generalization builds on
the fact that usual diff

D(A,B)

is by definition the same as combined diff

D(A,[B]),

so if we could rework the code for common case and make it be not slower
for nparent=1 case, usual diff(t1,t2) generation will not be slower, and
multiparent diff tree-walker would greatly benefit generating
combine-diff.

What we do is as follows:

1) diff tree-walker ll_diff_tree_sha1() is internally reworked to be
   a paths generator (new name diff_tree_paths()), with each generated path
   being `struct combine_diff_path` with info for path, new sha1,mode and for
   every parent which sha1,mode it was in it.

2) From that info, we can still generate usual diff queue with
   struct diff_filepairs, via "exporting" generated
   combine_diff_path, if we know we run for nparent=1 case.
   (see emit_diff() which is now named emit_diff_first_parent_only())

3) In order for diff_can_quit_early(), which checks

       DIFF_OPT_TST(opt, HAS_CHANGES))

   to work, that exporting have to be happening not in bulk, but
   incrementally, one diff path at a time.

   For such consumers, there is a new callback in diff_options
   introduced:

       ->pathchange(opt, struct combine_diff_path *)

   which, if set to !NULL, is called for every generated path.

   (see new compat ll_diff_tree_sha1() wrapper around new paths
    generator for setup)

4) The paths generation itself, is reworked from previous
   ll_diff_tree_sha1() code according to "D(A,P1...Pn) calculation
   scheme" provided above:

   On the start we allocate [nparent] arrays in place what was
   earlier just for one parent tree.

   then we just generalize loops, and comparison according to the
   algorithm.

Some notes(*):

1) alloca(), for small arrays, is used for "runs not slower for
   nparent=1 case than before" goal - if we change it to xmalloc()/free()
   the timings get ~1% worse. For alloca() we use just-introduced
   xalloca/xalloca_free compatibility wrappers, so it should not be a
   portability problem.

2) For every parent tree, we need to keep a tag, whether entry from that
   parent equals to entry from minimal parent. For performance reasons I'm
   keeping that tag in entry's mode field in unused bit - see S_IFXMIN_NEQ.
   Not doing so, we'd need to alloca another [nparent] array, which hurts
   performance.

3) For emitted paths, memory could be reused, if we know the path was
   processed via callback and will not be needed later. We use efficient
   hand-made realloc-style path_appendnew(), that saves us from ~1-1.5%
   of potential additional slowdown.

4) goto(s) are used in several places, as the code executes a little bit
   faster with lowered register pressure.

Also

- we should now check for FIND_COPIES_HARDER not only when two entries
  names are the same, and their hashes are equal, but also for a case,
  when a path was removed from some of all parents having it.

  The reason is, if we don't, that path won't be emitted at all (see
  "a > xi" case), and we'll just skip it, and FIND_COPIES_HARDER wants
  all paths - with diff or without - to be emitted, to be later analyzed
  for being copies sources.

  The new check is only necessary for nparent >1, as for nparent=1 case
  xmin_eqtotal always =1 =nparent, and a path is always added to diff as
  removal.

~~~~~~~~

Timings for

    # without -c, i.e. testing only nparent=1 case
    `git log --raw --no-abbrev --no-renames`

before and after the patch are as follows:

                navy.git        linux.git v3.10..v3.11

    before      0.611s          1.889s
    after       0.619s          1.907s
    slowdown    1.3%            0.9%

This timings show we did no harm to usual diff(tree1,tree2) generation.
From the table we can see that we actually did ~1% slowdown, but I think
I've "earned" that 1% in the previous patch ("tree-diff: reuse base
str(buf) memory on sub-tree recursion", HEAD~~) so for nparent=1 case,
net timings stays approximately the same.

The output also stayed the same.

(*) If we revert 1)-4) to more usual techniques, for nparent=1 case,
    we'll get ~2-2.5% of additional slowdown, which I've tried to avoid, as
   "do no harm for nparent=1 case" rule.

For linux.git, combined diff will run an order of magnitude faster and
appropriate timings will be provided in the next commit, as we'll be
taking advantage of the new diff tree-walker for combined-diff
generation there.

P.S. and combined diff is not some exotic/for-play-only stuff - for
example for a program I write to represent Git archives as readonly
filesystem, there is initial scan with

    `git log --reverse --raw --no-abbrev --no-renames -c`

to extract log of what was created/changed when, as a result building a
map

    {}  sha1    ->  in which commit (and date) a content was added

that `-c` means also show combined diff for merges, and without them, if
a merge is non-trivial (merges changes from two parents with both having
separate changes to a file), or an evil one, the map will not be full,
i.e. some valid sha1 would be absent from it.

That case was my initial motivation for combined diffs speedup.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-07 14:40:46 -07:00
Junio C Hamano
b6de0c633e Merge branch 'nd/tag-version-sort'
Allow v1.9.0 sorted before v1.10.0 in "git tag --list" output.

* nd/tag-version-sort:
  tag: support --sort=<spec>
2014-03-21 12:47:39 -07:00
Junio C Hamano
8aac6c97e8 Merge branch 'jk/commit-dates-parsing-fix' into maint
Codepaths that parse timestamps in commit objects have been
tightened.

* jk/commit-dates-parsing-fix:
  show_ident_date: fix tz range check
  log: do not segfault on gmtime errors
  log: handle integer overflow in timestamps
  date: check date overflow against time_t
  fsck: report integer overflow in author timestamps
  t4212: test bogus timestamps with git-log
2014-03-18 14:04:01 -07:00
Junio C Hamano
6d011b8e3f Merge branch 'bk/refresh-missing-ok-in-merge-recursive' into maint
"merge-recursive" was broken in 1.7.7 era and stopped working in an
empty (temporary) working tree, when there are renames involved.
This has been corrected.

* bk/refresh-missing-ok-in-merge-recursive:
  merge-recursive.c: tolerate missing files while refreshing index
  read-cache.c: extend make_cache_entry refresh flag with options
  read-cache.c: refactor --ignore-missing implementation
  t3030-merge-recursive: test known breakage with empty work tree
2014-03-18 14:02:38 -07:00
Junio C Hamano
3e30cb0fbf Merge branch 'mh/replace-refs-variable-rename'
* mh/replace-refs-variable-rename:
  Document some functions defined in object.c
  Add docstrings for lookup_replace_object() and do_lookup_replace_object()
  rename read_replace_refs to check_replace_refs
2014-03-14 14:27:06 -07:00
Junio C Hamano
060be00621 Merge branch 'mh/object-code-cleanup'
* mh/object-code-cleanup:
  sha1_file.c: document a bunch of functions defined in the file
  sha1_file_name(): declare to return a const string
  find_pack_entry(): document last_found_pack
  replace_object: use struct members instead of an array
2014-03-14 14:26:29 -07:00
Junio C Hamano
3c83b080e4 Merge branch 'jk/commit-dates-parsing-fix'
Tighten codepaths that parse timestamps in commit objects.

* jk/commit-dates-parsing-fix:
  show_ident_date: fix tz range check
  log: do not segfault on gmtime errors
  log: handle integer overflow in timestamps
  date: check date overflow against time_t
  fsck: report integer overflow in author timestamps
  t4212: test bogus timestamps with git-log
2014-03-14 14:25:44 -07:00
Junio C Hamano
08f36302b5 Merge branch 'ks/config-file-stdin'
"git config" learned to read from the standard input when "-" is
given as the value to its "--file" parameter (attempting an
operation to update the configuration in the standard input of
course is rejected).

* ks/config-file-stdin:
  config: teach "git config --file -" to read from the standard input
  config: change git_config_with_options() interface
  builtin/config.c: rename check_blob_write() -> check_write()
  config: disallow relative include paths from blobs
2014-03-14 14:24:40 -07:00
Junio C Hamano
053a6b1807 Merge branch 'jn/add-2.0-u-A-sans-pathspec'
"git add -u" and "git add -A" without any pathspec is a tree-wide
operation now, even when they are run in a subdirectory of the
working tree.
2014-03-07 15:14:02 -08:00
Junio C Hamano
4c4ac4db2c Merge branch 'nd/daemonize-gc'
Allow running "gc --auto" in the background.

* nd/daemonize-gc:
  gc: config option for running --auto in background
  daemon: move daemonize() to libgit.a
2014-03-05 15:06:39 -08:00