Commit Graph

932 Commits

Author SHA1 Message Date
Junio C Hamano
abecddea25 Merge branch 'jc/diff-ws-error-highlight'
A hotfix to a new feature in 2.5.0-rc.

* jc/diff-ws-error-highlight:
  diff: parse ws-error-highlight option more strictly
2015-07-15 12:30:14 -07:00
René Scharfe
3f4f17b51b diff: parse ws-error-highlight option more strictly
Check if a matched token is followed by a delimiter before advancing the
pointer arg.  This avoids accepting composite words like "allnew" or
"defaultcontext" and misparsing them as "new" or "context".

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-07-12 09:55:23 -07:00
Junio C Hamano
db65170ee5 Merge branch 'jk/color-diff-plain-is-context'
"color.diff.plain" was a misnomer; give it 'color.diff.context' as
a more logical synonym.

* jk/color-diff-plain-is-context:
  diff.h: rename DIFF_PLAIN color slot to DIFF_CONTEXT
  diff: accept color.diff.context as a synonym for "plain"
2015-06-11 09:29:53 -07:00
Junio C Hamano
709cd912d4 Merge branch 'jc/diff-ws-error-highlight'
Allow whitespace breakages in deleted and context lines to be also
painted in the output.

* jc/diff-ws-error-highlight:
  diff.c: --ws-error-highlight=<kind> option
  diff.c: add emit_del_line() and emit_context_line()
  t4015: separate common setup and per-test expectation
  t4015: modernise style
2015-06-11 09:29:51 -07:00
Jeff King
8dbf3eb685 diff.h: rename DIFF_PLAIN color slot to DIFF_CONTEXT
The latter is a much more descriptive name (and we support
"color.diff.context" now). This also updates the name of any
local variables which were used to store the color.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-05-27 13:54:42 -07:00
Jeff King
74b15bfbf6 diff: accept color.diff.context as a synonym for "plain"
The term "plain" is a bit ambiguous; let's allow the more
specific "context", but keep "plain" around for
compatibility.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-05-27 13:54:37 -07:00
Junio C Hamano
b8767f791c diff.c: --ws-error-highlight=<kind> option
Traditionally, we only cared about whitespace breakages introduced
in new lines.  Some people want to paint whitespace breakages on old
lines, too.  When they see a whitespace breakage on a new line, they
can spot the same kind of whitespace breakage on the corresponding
old line and want to say "Ah, those breakages are there but they
were inherited from the original, so let's not touch them for now."

Introduce `--ws-error-highlight=<kind>` option, that lets them pass
a comma separated list of `old`, `new`, and `context` to specify
what lines to highlight whitespace errors on.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-05-26 23:00:01 -07:00
Junio C Hamano
0e383e185a diff.c: add emit_del_line() and emit_context_line()
Traditionally, we only had emit_add_line() helper, which knows how
to find and paint whitespace breakages on the given line, because we
only care about whitespace breakages introduced in new lines.  The
context lines and old (i.e. deleted) lines are emitted with a
simpler emit_line_0() that paints the entire line in plain or old
colors.

Identify callers of emit_line_0() that show deleted lines and
context lines, have them call new helpers, emit_del_line() and
emit_context_line(), so that we can later tweak what is done to
these two classes of lines.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-05-26 22:13:02 -07:00
Junio C Hamano
6902c4da58 Merge branch 'rs/deflate-init-cleanup'
Code simplification.

* rs/deflate-init-cleanup:
  zlib: initialize git_zstream in git_deflate_init{,_gzip,_raw}
2015-03-17 16:01:26 -07:00
Junio C Hamano
b6488fe191 Merge branch 'mk/diff-shortstat-dirstat-fix'
"git diff --shortstat --dirstat=changes" showed a dirstat based on
lines that was never asked by the end user in addition to the
dirstat that the user asked for.

* mk/diff-shortstat-dirstat-fix:
  diff --shortstat --dirstat: remove duplicate output
2015-03-06 15:02:29 -08:00
René Scharfe
9a6f1287fb zlib: initialize git_zstream in git_deflate_init{,_gzip,_raw}
Clear the git_zstream variable at the start of git_deflate_init() etc.
so that callers don't have to do that.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-03-05 15:46:03 -08:00
Mårten Kongstad
ab27389aff diff --shortstat --dirstat: remove duplicate output
When --shortstat is used in conjunction with --dirstat=changes, git diff will
output the dirstat information twice: first as calculated by the 'lines'
algorithm, then as calculated by the 'changes' algorithm:

    $ git diff --dirstat=changes,10 --shortstat v2.2.0..v2.2.1
     23 files changed, 453 insertions(+), 54 deletions(-)
      33.5% Documentation/RelNotes/
      26.2% t/
      46.6% Documentation/RelNotes/
      16.6% t/

The same duplication happens for --shortstat together with --dirstat=files, but
not for --shortstat together with --dirstat=lines.

Limit output to only include one dirstat part, calculated as specified
by the --dirstat parameter. Also, add test for this.

Signed-off-by: Mårten Kongstad <marten.kongstad@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2015-03-02 11:31:27 -08:00
Junio C Hamano
b946576839 Merge branch 'jn/parse-config-slot'
Code cleanup.

* jn/parse-config-slot:
  color_parse: do not mention variable name in error message
  pass config slots as pointers instead of offsets
2014-10-20 12:23:48 -07:00
Jeff King
f6c5a2968c color_parse: do not mention variable name in error message
Originally the color-parsing function was used only for
config variables. It made sense to pass the variable name so
that the die() message could be something like:

  $ git -c color.branch.plain=bogus branch
  fatal: bad color value 'bogus' for variable 'color.branch.plain'

These days we call it in other contexts, and the resulting
error messages are a little confusing:

  $ git log --pretty='%C(bogus)'
  fatal: bad color value 'bogus' for variable '--pretty format'

  $ git config --get-color foo.bar bogus
  fatal: bad color value 'bogus' for variable 'command line'

This patch teaches color_parse to complain only about the
value, and then return an error code. Config callers can
then propagate that up to the config parser, which mentions
the variable name. Other callers can provide a custom
message. After this patch these three cases now look like:

  $ git -c color.branch.plain=bogus branch
  error: invalid color value: bogus
  fatal: unable to parse 'color.branch.plain' from command-line config

  $ git log --pretty='%C(bogus)'
  error: invalid color value: bogus
  fatal: unable to parse --pretty format

  $ git config --get-color foo.bar bogus
  error: invalid color value: bogus
  fatal: unable to parse default color value

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-10-14 11:01:21 -07:00
Junio C Hamano
bedd3b4b7b Merge branch 'nd/large-blobs'
Teach a few codepaths to punt (instead of dying) when large blobs
that would not fit in core are involved in the operation.

* nd/large-blobs:
  diff: shortcut for diff'ing two binary SHA-1 objects
  diff --stat: mark any file larger than core.bigfilethreshold binary
  diff.c: allow to pass more flags to diff_populate_filespec
  sha1_file.c: do not die failing to malloc in unpack_compressed_entry
  wrapper.c: introduce gentle xmallocz that does not die()
2014-09-11 10:33:33 -07:00
René Scharfe
d318027932 run-command: introduce CHILD_PROCESS_INIT
Most struct child_process variables are cleared using memset first after
declaration.  Provide a macro, CHILD_PROCESS_INIT, that can be used to
initialize them statically instead.  That's shorter, doesn't require a
function call and is slightly more readable (especially given that we
already have STRBUF_INIT, ARGV_ARRAY_INIT etc.).

Helped-by: Johannes Sixt <j6t@kdbg.org>
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-08-20 09:53:37 -07:00
Nguyễn Thái Ngọc Duy
1aaf69e669 diff: shortcut for diff'ing two binary SHA-1 objects
If we are given two SHA-1 and asked to determine if they are different
(but not _what_ differences), we know right away by comparing SHA-1.

A side effect of this patch is, because large files are marked binary,
diff-tree will not need to unpack them. 'diff-index --cached' will not
either. But 'diff-files' still does.

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-08-18 10:16:55 -07:00
Nguyễn Thái Ngọc Duy
6bf3b81348 diff --stat: mark any file larger than core.bigfilethreshold binary
Too large files may lead to failure to allocate memory. If it happens
here, it could impact quite a few commands that involve
diff. Moreover, too large files are inefficient to compare anyway (and
most likely non-text), so mark them binary and skip looking at their
content.

Noticed-by: Dale R. Worley <worley@alum.mit.edu>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-08-18 10:16:45 -07:00
Nguyễn Thái Ngọc Duy
8e5dd3d654 diff.c: allow to pass more flags to diff_populate_filespec
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-08-18 10:16:35 -07:00
Junio C Hamano
cfececfe1f Merge branch 'bg/xcalloc-nmemb-then-size' into maint
* bg/xcalloc-nmemb-then-size:
  transport-helper.c: rearrange xcalloc arguments
  remote.c: rearrange xcalloc arguments
  reflog-walk.c: rearrange xcalloc arguments
  pack-revindex.c: rearrange xcalloc arguments
  notes.c: rearrange xcalloc arguments
  imap-send.c: rearrange xcalloc arguments
  http-push.c: rearrange xcalloc arguments
  diff.c: rearrange xcalloc arguments
  config.c: rearrange xcalloc arguments
  commit.c: rearrange xcalloc arguments
  builtin/remote.c: rearrange xcalloc arguments
  builtin/ls-remote.c: rearrange xcalloc arguments
2014-07-22 10:25:17 -07:00
René Scharfe
cedc61a998 strbuf: use strbuf_addstr() for adding C strings
Avoid code duplication and let strbuf_addstr() call strlen() for us.

Signed-off-by: Rene Scharfe <l.s.r@web.de>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-07-17 13:33:52 -07:00
Junio C Hamano
cb4575fb18 Merge branch 'jk/diff-follow-must-take-one-pathspec' into maint
"git format-patch" did not enforce the rule that the "--follow"
option from the log/diff family of commands must be used with
exactly one pathspec.

* jk/diff-follow-must-take-one-pathspec:
  move "--follow needs one pathspec" rule to diff_setup_done
2014-06-25 11:47:23 -07:00
Jeff King
0539cc0038 stat_opt: check extra strlen call
As in earlier commits, the diff option parser uses
starts_with to find that an argument starts with "--stat-",
and then adds strlen("stat-") to find the rest of the
option.

However, in this case the starts_with and the strlen are
separated across functions, making it easy to call the
latter without the former. Let's use skip_prefix instead of
raw pointer arithmetic to catch such a case.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-20 10:45:19 -07:00
Jeff King
95b567c7c3 use skip_prefix to avoid repeating strings
It's a common idiom to match a prefix and then skip past it
with strlen, like:

  if (starts_with(foo, "bar"))
	  foo += strlen("bar");

This avoids magic numbers, but means we have to repeat the
string (and there is no compiler check that we didn't make a
typo in one of the strings).

We can use skip_prefix to handle this case without repeating
ourselves.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-20 10:44:45 -07:00
Jeff King
ae021d8791 use skip_prefix to avoid magic numbers
It's a common idiom to match a prefix and then skip past it
with a magic number, like:

  if (starts_with(foo, "bar"))
	  foo += 3;

This is easy to get wrong, since you have to count the
prefix string yourself, and there's no compiler check if the
string changes.  We can use skip_prefix to avoid the magic
numbers here.

Note that some of these conversions could be much shorter.
For example:

  if (starts_with(arg, "--foo=")) {
	  bar = arg + 6;
	  continue;
  }

could become:

  if (skip_prefix(arg, "--foo=", &bar))
	  continue;

However, I have left it as:

  if (skip_prefix(arg, "--foo=", &v)) {
	  bar = v;
	  continue;
  }

to visually match nearby cases which need to actually
process the string. Like:

  if (skip_prefix(arg, "--foo=", &v)) {
	  bar = atoi(v);
	  continue;
  }

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-20 10:44:45 -07:00
Jeff King
9e1a5ebe52 parse_diff_color_slot: drop ofs parameter
This function originally took a whole config variable name
("var") and an offset ("ofs"). It checked "var+ofs" against
each color slot, but reported errors using the whole "var".

However, since 8b8e862 (ignore unknown color configuration,
2009-12-12), it returns -1 rather than printing its own
error, and therefore only cares about var+ofs. We can drop
the ofs parameter and teach its sole caller to derive the
pointer itself.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-06-18 14:56:17 -07:00
Junio C Hamano
a634a6d209 Merge branch 'bg/xcalloc-nmemb-then-size'
Like calloc(3), xcalloc() takes nmemb and then size.

* bg/xcalloc-nmemb-then-size:
  transport-helper.c: rearrange xcalloc arguments
  remote.c: rearrange xcalloc arguments
  reflog-walk.c: rearrange xcalloc arguments
  pack-revindex.c: rearrange xcalloc arguments
  notes.c: rearrange xcalloc arguments
  imap-send.c: rearrange xcalloc arguments
  http-push.c: rearrange xcalloc arguments
  diff.c: rearrange xcalloc arguments
  config.c: rearrange xcalloc arguments
  commit.c: rearrange xcalloc arguments
  builtin/remote.c: rearrange xcalloc arguments
  builtin/ls-remote.c: rearrange xcalloc arguments
2014-06-16 12:17:50 -07:00
Junio C Hamano
b0e2c999af Merge branch 'jk/diff-follow-must-take-one-pathspec'
* jk/diff-follow-must-take-one-pathspec:
  move "--follow needs one pathspec" rule to diff_setup_done
2014-06-16 10:07:09 -07:00
Junio C Hamano
6779e43b0d Merge branch 'jk/external-diff-use-argv-array'
Code clean-up (and a bugfix which has been merged for 2.0).

* jk/external-diff-use-argv-array:
  run_external_diff: refactor cmdline setup logic
  run_external_diff: hoist common bits out of conditional
  run_external_diff: drop fflush(NULL)
  run_external_diff: clean up error handling
  run_external_diff: use an argv_array for the environment
2014-06-03 12:06:43 -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
Brian Gesiak
1a4927c5c5 diff.c: rearrange xcalloc arguments
xcalloc() takes two arguments: the number of elements and their size.
diffstat_add() passes the arguments in reverse order, passing the
size of a diffstat_file*, followed by the number of diffstat_file* to
be allocated.

Rearrange them so they are in the correct order.

Signed-off-by: Brian Gesiak <modocache@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-05-27 14:02:03 -07:00
Jeff King
dd63f169d9 move "--follow needs one pathspec" rule to diff_setup_done
Because of the way "--follow" is implemented, we must have
exactly one pathspec. "git log" enforces this restriction,
but other users of the revision traversal code do not. For
example, "git format-patch --follow" will segfault during
try_to_follow_renames, as we have no pathspecs at all.

We can push this check down into diff_setup_done, which is
probably a better place anyway. It is the diff code that
introduces this restriction, so other parts of the code
should not need to care themselves.

Reported-by: "Michael S. Tsirkin" <mst@redhat.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-05-20 11:09:03 -07:00
Junio C Hamano
5f11a7aad0 Merge branch 'jk/external-diff-use-argv-array' (early part)
Crash fix for codepath that miscounted the necessary size for an
array when spawning an external diff program.

* 'jk/external-diff-use-argv-array' (early part):
  run_external_diff: use an argv_array for the command line
2014-04-28 15:47:35 -07:00
Jeff King
f3efe78782 run_external_diff: refactor cmdline setup logic
The current logic makes it hard to see what gets put onto
the command line in which cases. Pulling out a helper
function lets us see that we have two sets of file data, and
the second set either uses the original name, or the "other"
renamed/copy name.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-21 10:32:19 -07:00
Jeff King
0d4217d92e run_external_diff: hoist common bits out of conditional
Whether we have diff_filespecs to give to the diff command
or not, we always are going to run the program and pass it
the pathname. Let's pull that duplicated part out of the
conditional to make it more obvious.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-21 10:32:07 -07:00
Jeff King
5b88caa417 run_external_diff: drop fflush(NULL)
This fflush was added in d5535ec (Use run_command() to spawn
external diff programs instead of fork/exec., 2007-10-19),
because flushing buffers before forking is a good habit.

But later, 7d0b18a (Add output flushing before fork(),
2008-08-04) added it to the generic run-command interface,
meaning that our flush here is redundant.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-21 10:31:51 -07:00
Jeff King
89294d143d run_external_diff: clean up error handling
When the external diff reports an error, we try to clean up
and die. However, we can make this process a bit simpler:

  1. We do not need to bother freeing memory, since we are
     about to exit.  Nor do we need to clean up our
     tempfiles, since the atexit() handler will do it for
     us. So we can die as soon as we see the error.

  3. We can just call die() rather than fprintf/exit. This
     does technically change our exit code, but the exit
     code of "1" is not meaningful here. In fact, it is
     probably wrong, since "1" from diff usually means
     "completed successfully, but there were differences".

And while we're there, we can mark the error message for
translation, and drop the full stop at the end to make it
more like our other messages.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-21 10:31:36 -07:00
Jeff King
ae049c955c run_external_diff: use an argv_array for the environment
We currently use static buffers and a static array for
formatting the environment passed to the external diff.
There's nothing wrong in the code, but it is much easier to
verify that it is correct if we use a dynamic argv_array.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-21 10:30:33 -07:00
Jeff King
82fbf269b9 run_external_diff: use an argv_array for the command line
We currently generate the command-line for the external
command using a fixed-length array of size 10. But if there
is a rename, we actually need 11 elements (10 items, plus a
NULL), and end up writing a random NULL onto the stack.

Rather than bump the limit, let's just use an argv_array, which
makes this sort of error impossible.

Noticed-by: Max L <infthi.inbox@gmail.com>
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-21 10:29:50 -07:00
Jiang Xin
d1d96a82bb i18n: remove obsolete comments for translators in diffstat generation
Since we do not translate diffstat any more, remove the obsolete comments.

Signed-off-by: Jiang Xin <worldhello.net@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-17 11:09:56 -07:00
Junio C Hamano
d59c12d7ad Merge branch 'jl/nor-or-nand-and'
Eradicate mistaken use of "nor" (that is, essentially "nor" used
not in "neither A nor B" ;-)) from in-code comments, command output
strings, and documentations.

* jl/nor-or-nand-and:
  code and test: fix misuses of "nor"
  comments: fix misuses of "nor"
  contrib: fix misuses of "nor"
  Documentation: fix misuses of "nor"
2014-04-08 12:00:28 -07:00
Kirill Smelkov
7195fbfaf5 combine-diff: speed it up, by using multiparent diff tree-walker directly
As was recently shown in "combine-diff: optimize
combine_diff_path sets intersection", combine-diff runs very slowly. In
that commit we optimized paths sets intersection, but that accounted
only for ~ 25% of the slowness, and as my tracing showed, for linux.git
v3.10..v3.11, for merges 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).

In previous commit, we described the problem in more details, and
reworked the diff tree-walker to be general one - i.e. to work in
multiple parent case too. Now is the time to take advantage of it for
finding paths for combine diff.

The implementation is straightforward - if we know, we can get generated
diff paths directly, and at present that means no diff filtering or
rename/copy detection was requested(*), we can call multiparent tree-walker
directly and get ready paths.

(*) because e.g. at present, all diffcore transformations work on
    diff_filepair queues, but in the future, that limitation can be
    lifted, if filters would operate directly on combine_diff_paths.

Timings for `git log --raw --no-abbrev --no-renames` without `-c` ("git log")
and with `-c` ("git log -c") and with `-c --merges` ("git log -c --merges")
before and after the patch are as follows:

                linux.git v3.10..v3.11

            log     log -c     log -c --merges

    before  1.9s    16.4s      15.2s
    after   1.9s     2.4s       1.1s

The result stayed the same.

Signed-off-by: Kirill Smelkov <kirr@mns.spb.ru>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-04-07 14:41:49 -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
Justin Lebar
01689909eb comments: fix misuses of "nor"
Signed-off-by: Justin Lebar <jlebar@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-31 15:29:27 -07:00
Junio C Hamano
a5aca6e883 Merge branch 'tr/diff-submodule-no-reuse-worktree' into maint
"git diff --external-diff" incorrectly fed the submodule directory
in the working tree to the external diff driver when it knew it is
the same as one of the versions being compared.

* tr/diff-submodule-no-reuse-worktree:
  diff: do not reuse_worktree_file for submodules
2014-03-18 14:03:41 -07:00
Junio C Hamano
34120a5fb5 Merge branch 'nd/diff-quiet-stat-dirty' into maint
"git diff --quiet -- pathspec1 pathspec2" sometimes did not return
correct status value.

* nd/diff-quiet-stat-dirty:
  diff: do not quit early on stat-dirty files
  diff.c: move diffcore_skip_stat_unmatch core logic out for reuse later
2014-03-18 13:59:56 -07:00
Junio C Hamano
6f75e48323 Merge branch 'rm/strchrnul-not-strlen'
* rm/strchrnul-not-strlen:
  use strchrnul() in place of strchr() and strlen()
2014-03-18 13:51:18 -07:00
Junio C Hamano
fe9122a352 Merge branch 'dd/use-alloc-grow'
Replace open-coded reallocation with ALLOC_GROW() macro.

* dd/use-alloc-grow:
  sha1_file.c: use ALLOC_GROW() in pretend_sha1_file()
  read-cache.c: use ALLOC_GROW() in add_index_entry()
  builtin/mktree.c: use ALLOC_GROW() in append_to_tree()
  attr.c: use ALLOC_GROW() in handle_attr_line()
  dir.c: use ALLOC_GROW() in create_simplify()
  reflog-walk.c: use ALLOC_GROW()
  replace_object.c: use ALLOC_GROW() in register_replace_object()
  patch-ids.c: use ALLOC_GROW() in add_commit()
  diffcore-rename.c: use ALLOC_GROW()
  diff.c: use ALLOC_GROW()
  commit.c: use ALLOC_GROW() in register_commit_graft()
  cache-tree.c: use ALLOC_GROW() in find_subtree()
  bundle.c: use ALLOC_GROW() in add_to_ref_list()
  builtin/pack-objects.c: use ALLOC_GROW() in check_pbase_path()
2014-03-18 13:50:21 -07:00
Junio C Hamano
481e6aaacc Merge branch 'tr/diff-submodule-no-reuse-worktree'
"git diff --external-diff" incorrectly fed the submodule directory
in the working tree to the external diff driver when it knew it is
the same as one of the versions being compared.

* tr/diff-submodule-no-reuse-worktree:
  diff: do not reuse_worktree_file for submodules
2014-03-14 14:25:20 -07:00
Rohit Mani
2c5495f7b6 use strchrnul() in place of strchr() and strlen()
Avoid scanning strings twice, once with strchr() and then with
strlen(), by using strchrnul().

Helped-by: Junio C Hamano <gitster@pobox.com>
Signed-off-by: Rohit Mani <rohit.mani@outlook.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
2014-03-10 08:35:30 -07:00