Our word-diff does not look at the -/+ lines generated by xdiff at all
(because they are not real lines to show the user, but just the
tokenized words split into lines). Instead we use the line numbers from
the hunk headers to index our own data structure.
As a result, our xdi_diff_outf() callback throws away all lines except
hunk headers. We can instead use a hunk callback, which has two
benefits:
1. We don't have to re-parse the generated hunk header line, but can
use the passed parameters directly.
2. By setting our line callback to NULL, we can tell xdiff-interface
that it does not even need to bother generating the other lines,
saving a small amount of work.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Some callers of xdi_diff_outf() do not look at the generated hunk header
lines at all. By plugging in a no-op hunk callback, this tells xdiff not
to even bother formatting them.
This patch introduces a stock no-op callback and uses it with a few
callers whose line callbacks explicitly ignore hunk headers (because
they look only for +/- lines).
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The previous commit taught xdiff to optionally provide the hunk header
data to a specialized callback. But most users of xdiff actually use our
more convenient xdi_diff_outf() helper, which ensures that our callbacks
are always fed whole lines.
Let's plumb the special hunk-callback through this interface, too. It
will follow the same rule as xdiff when the hunk callback is NULL (i.e.,
continue to pass a stringified hunk header to the line callback). Since
we add NULL to each caller, there should be no behavior change yet.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The xdiff library always emits hunk header lines to our callbacks as
formatted strings like "@@ -a,b +c,d @@\n". This is convenient if we're
going to output a diff, but less so if we actually need to compute using
those numbers, which requires re-parsing the line.
In preparation for moving away from this, let's teach xdiff a new
callback function which gets the broken-out hunk information. To help
callers that don't want to use this new callback, if it's NULL we'll
continue to format the hunk header into a string.
Note that this function renames the "outf" callback to "out_line", as
well. This isn't strictly necessary, but helps in two ways:
1. Now that there are two callbacks, it's nice to use more descriptive
names.
2. Many callers did not zero the emit_callback_data struct, and needed
to be modified to set ecb.out_hunk to NULL. By changing the name of
the existing struct member, that guarantees that any new callers
from in-flight topics will break the build and be examined
manually.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This should make these functions easier to find and cache.h less
overwhelming to read.
In particular, this moves:
- read_object_file
- oid_object_info
- write_object_file
As a result, most of the codebase needs to #include object-store.h.
In this patch the #include is only added to files that would fail to
compile otherwise. It would be better to #include wherever
identifiers from the header are used. That can happen later
when we have better tooling for it.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Convert read_sha1_file to take a pointer to struct object_id and rename
it read_object_file. Do the same for read_sha1_file_extended.
Convert one use in grep.c to use the new function without any other code
change, since the pointer being passed is a void pointer that is already
initialized with a pointer to struct object_id. Update the declaration
and definitions of the modified functions, and apply the following
semantic patch to convert the remaining callers:
@@
expression E1, E2, E3;
@@
- read_sha1_file(E1.hash, E2, E3)
+ read_object_file(&E1, E2, E3)
@@
expression E1, E2, E3;
@@
- read_sha1_file(E1->hash, E2, E3)
+ read_object_file(E1, E2, E3)
@@
expression E1, E2, E3, E4;
@@
- read_sha1_file_extended(E1.hash, E2, E3, E4)
+ read_object_file_extended(&E1, E2, E3, E4)
@@
expression E1, E2, E3, E4;
@@
- read_sha1_file_extended(E1->hash, E2, E3, E4)
+ read_object_file_extended(E1, E2, E3, E4)
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This will turn out to be useful in a later patch.
xdl_recmatch is exported in xdiff/xutils.h, to be used by various
xdiff/*.c files, but not outside of xdiff/. This one makes it available
to the outside, too.
While at it, add documentation.
Signed-off-by: Stefan Beller <sbeller@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Fix configuration codepath to pay proper attention to commondir
that is used in multi-worktree situation, and isolate config API
into its own header file.
* bw/config-h:
config: don't implicitly use gitdir or commondir
config: respect commondir
setup: teach discover_git_directory to respect the commondir
config: don't include config.h by default
config: remove git_config_iter
config: create config.h
Stop including config.h by default in cache.h. Instead only include
config.h in those files which require use of the config system.
Signed-off-by: Brandon Williams <bmwill@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Some codepaths in "git diff" used regexec(3) on a buffer that was
mmap(2)ed, which may not have a terminating NUL, leading to a read
beyond the end of the mapped region. This was fixed by introducing
a regexec_buf() helper that takes a <ptr,len> pair with REG_STARTEND
extension.
* js/regexec-buf:
regex: use regexec_buf()
regex: add regexec_buf() that can work on a non NUL-terminated string
regex: -G<pattern> feeds a non NUL-terminated string to regexec() and fails
The new regexec_buf() function operates on buffers with an explicitly
specified length, rather than NUL-terminated strings.
We need to use this function whenever the buffer we want to pass to
regexec(3) may have been mmap(2)ed (and is hence not NUL-terminated).
Note: the original motivation for this patch was to fix a bug where
`git diff -G <regex>` would crash. This patch converts more callers,
though, some of which allocated to construct NUL-terminated strings,
or worse, modified buffers to temporarily insert NULs while calling
regexec(3). By converting them to use regexec_buf(), the code has
become much cleaner.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Since all of its callers have been updated, convert read_mmblob to take
a pointer to struct object_id.
Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The function trim_common_tail() exits early if context lines are
requested. If -U0 and -W are specified together then it can still trim
context lines that might belong to a changed function. As a result
that function is shown incompletely.
Fix that by calling trim_common_tail() only if no function context or
fixed context is requested. The parameter ctx is no longer needed now;
remove it.
While at it fix an outdated comment as well.
Signed-off-by: Rene Scharfe <l.s.r@web.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Each of these cases can be converted to use ALLOC_ARRAY or
REALLOC_ARRAY, which has two advantages:
1. It automatically checks the array-size multiplication
for overflow.
2. It always uses sizeof(*array) for the element-size,
so that it can never go out of sync with the declared
type of the array.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The xdiff code is not prepared to handle extremely large
files. It uses "int" in many places, which can overflow if
we have a very large number of lines or even bytes in our
input files. This can cause us to produce incorrect diffs,
with no indication that the output is wrong. Or worse, we
may even underallocate a buffer whose size is the result of
an overflowing addition.
We're much better off to tell the user that we cannot diff
or merge such a large file. This patch covers both cases,
but in slightly different ways:
1. For merging, we notice the large file and cleanly fall
back to a binary merge (which is effectively "we cannot
merge this").
2. For diffing, we make the binary/text distinction much
earlier, and in many different places. For this case,
we'll use the xdi_diff as our choke point, and reject
any diff there before it hits the xdiff code.
This means in most cases we'll die() immediately after.
That's not ideal, but in practice we shouldn't
generally hit this code path unless the user is trying
to do something tricky. We already consider files
larger than core.bigfilethreshold to be binary, so this
code would only kick in when that is circumvented
(either by bumping that value, or by using a
.gitattribute to mark a file as diffable).
In other words, we can avoid being "nice" here, because
there is already nice code that tries to do the right
thing. We are adding the suspenders to the nice code's
belt, so notice when it has been worked around (both to
protect the user from malicious inputs, and because it
is better to die() than generate bogus output).
The maximum size was chosen after experimenting with feeding
large files to the xdiff code. It's just under a gigabyte,
which leaves room for two obvious cases:
- a diff3 merge conflict result on files of maximum size X
could be 3*X plus the size of the markers, which would
still be only about 3G, which fits in a 32-bit int.
- some of the diff code allocates arrays of one int per
record. Even if each file consists only of blank lines,
then a file smaller than 1G will have fewer than 1G
records, and therefore the int array will fit in 4G.
Since the limit is arbitrary anyway, I chose to go under a
gigabyte, to leave a safety margin (e.g., we would not want
to overflow by allocating "(records + 1) * sizeof(int)" or
similar.
Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The config machinery already makes section and variable names
lowercase when parsing them, so using strcasecmp for comparison just
feels wasteful. No noticeable change intended.
Noticed-by: Jay Soffian <jaysoffian@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Generally, trailing space is removed from the string matched by the
xfuncname patterns. The exception is when the matched string exceeds the
length of the fixed-size buffer that it will be copied in to. But, a
string that exceeds the buffer can still contain trailing space in the
portion of the string that will be copied into the buffer. So, simplify
this code slightly, and just perform the trailing space removal always.
Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
xdi_diff_outf() overrides the structure members of its last parameter,
ignoring any value that callers pass in. It's no surprise then that all
callers pass a pointer to an uninitialized structure. They also don't
read it after the call, so the parameter is neither used for input nor
for output. Turn it into a local variable of xdi_diff_outf().
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Acked-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The following function is duplicated:
fill_mm
Move it to xdiff-interface.c and rename it 'read_mmblob', as suggested
by Junio C Hamano.
Also, change parameters order for consistency with read_mmfile().
Signed-off-by: Michael Lukashov <michael.lukashov@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
xdiff_set_find_func() is used to set user defined regular expressions
for finding function signatures. Add xdiff_clear_find_func(), which
frees the memory allocated by the former, making the API complete.
Also, use the new function in diff.c (the only call site of
xdiff_set_find_func()) to clean up after ourselves.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
These variables were unused and can be removed safely:
builtin-clone.c::cmd_clone(): use_local_hardlinks, use_separate_remote
builtin-fetch-pack.c::find_common(): len
builtin-remote.c::mv(): symref
diff.c::show_stats():show_stats(): total
diffcore-break.c::should_break(): base_size
fast-import.c::validate_raw_date(): date, sign
fsck.c::fsck_tree(): o_sha1, sha1
xdiff-interface.c::parse_num(): read_some
Signed-off-by: Benjamin Kramer <benny.kra@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* rs/blame:
blame: use xdi_diff_hunks(), get rid of struct patch
add xdi_diff_hunks() for callers that only need hunk lengths
Allow alternate "low-level" emit function from xdl_diff
Always initialize xpparam_t to 0
blame: inline get_patch()
Based on a patch by Brian Downing, this uses the xdiff emit_func feature
to implement xdi_diff_hunks(). It's a function that calls a callback for
each hunk of a diff, passing its lengths.
Signed-off-by: Rene Scharfe <rene.scharfe@lsrfire.ath.cx>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* maint:
t1301-shared-repo.sh: don't let a default ACL interfere with the test
git-check-attr(1): add output and example sections
xdiff-interface.c: strip newline (and cr) from line before pattern matching
t4018-diff-funcname: demonstrate end of line funcname matching flaw
t4018-diff-funcname: rework negated last expression test
Typo "does not exists" when git remote update remote.
remote.c: correct the check for a leading '/' in a remote name
Add testcase to ensure merging an early part of a branch is done properly
Conflicts:
t/t7600-merge.sh
POSIX doth sayeth:
"In the regular expression processing described in IEEE Std 1003.1-2001,
the <newline> is regarded as an ordinary character and both a period and
a non-matching list can match one. ... Those utilities (like grep) that
do not allow <newline>s to match are responsible for eliminating any
<newline> from strings before matching against the RE."
Thus far git has not been removing the trailing newline from strings matched
against regular expression patterns. This has the effect that (quoting
Jonathan del Strother) "... a line containing just 'FUNCNAME' (terminated by
a newline) will be matched by the pattern '^(FUNCNAME.$)' but not
'^(FUNCNAME$)'", and more simply not '^FUNCNAME$'.
Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
POSIX doth sayeth:
"In the regular expression processing described in IEEE Std 1003.1-2001,
the <newline> is regarded as an ordinary character and both a period and
a non-matching list can match one. ... Those utilities (like grep) that
do not allow <newline>s to match are responsible for eliminating any
<newline> from strings before matching against the RE."
Thus far git has not been removing the trailing newline from strings matched
against regular expression patterns. This has the effect that (quoting
Jonathan del Strother) "... a line containing just 'FUNCNAME' (terminated by
a newline) will be matched by the pattern '^(FUNCNAME.$)' but not
'^(FUNCNAME$)'", and more simply not '^FUNCNAME$'.
Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
* bc/master-diff-hunk-header-fix:
Clarify commit error message for unmerged files
Use strchrnul() instead of strchr() plus manual workaround
Use remove_path from dir.c instead of own implementation
Add remove_path: a function to remove as much as possible of a path
git-submodule: Fix "Unable to checkout" for the initial 'update'
Clarify how the user can satisfy stash's 'dirty state' check.
t4018-diff-funcname: test syntax of builtin xfuncname patterns
t4018-diff-funcname: test syntax of builtin xfuncname patterns
make "git remote" report multiple URLs
diff hunk pattern: fix misconverted "\{" tex macro introducers
diff: fix "multiple regexp" semantics to find hunk header comment
diff: use extended regexp to find hunk headers
diff: use extended regexp to find hunk headers
diff.*.xfuncname which uses "extended" regex's for hunk header selection
diff.c: associate a flag with each pattern and use it for compiling regex
diff.c: return pattern entry pointer rather than just the hunk header pattern
Conflicts:
builtin-merge-recursive.c
t/t7201-co.sh
xdiff-interface.h
* jc/better-conflict-resolution:
Fix AsciiDoc errors in merge documentation
git-merge documentation: describe how conflict is presented
checkout --conflict=<style>: recreate merge in a non-default style
checkout -m: recreate merge when checking out of unmerged index
git-merge-recursive: learn to honor merge.conflictstyle
merge.conflictstyle: choose between "merge" and "diff3 -m" styles
rerere: understand "diff3 -m" style conflicts with the original
rerere.c: use symbolic constants to keep track of parsing states
xmerge.c: "diff3 -m" style clips merge reduction level to EAGER or less
xmerge.c: minimum readability fixups
xdiff-merge: optionally show conflicts in "diff3 -m" style
xdl_fill_merge_buffer(): separate out a too deeply nested function
checkout --ours/--theirs: allow checking out one side of a conflicting merge
checkout -f: allow ignoring unmerged paths when checking out of the index
Conflicts:
Documentation/git-checkout.txt
builtin-checkout.c
builtin-merge-recursive.c
t/t7201-co.sh
When multiple regular expressions are concatenated with "\n", they were
traditionally AND'ed together, and only a line that matches _all_ of them
is taken as a match. This however is unwieldy when multiple regexp
feature is used to specify alternatives.
This fixes the semantics to take the first match. A nagative pattern, if
matches, makes the line to fail as before. A match with a positive
pattern will be the final match, and what it captures in $1 is used as the
hunk header comment.
We could write alternatives using "|" in ERE, but the machinery can only
use captured $1 as the hunk header comment (or $0 if there is no match in
$1), so you cannot write:
"junk ( A | B ) | garbage ( C | D )"
and expect both "junk" and "garbage" to get stripped with the existing
code. With this fix, you can write it as:
"junk ( A | B ) \n garbage ( C | D )"
and the way capture works would match the user expectation more
naturally.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* bc/maint-diff-hunk-header-fix:
diff.*.xfuncname which uses "extended" regex's for hunk header selection
diff.c: associate a flag with each pattern and use it for compiling regex
diff.c: return pattern entry pointer rather than just the hunk header pattern
Cosmetical command name fix
Start conforming code to "git subcmd" style part 3
t9700/test.pl: remove File::Temp requirement
t9700/test.pl: avoid bareword 'STDERR' in 3-argument open()
GIT 1.6.0.2
Fix some manual typos.
Use compatibility regex library also on FreeBSD
Use compatibility regex library also on AIX
Update draft release notes for 1.6.0.2
Use compatibility regex library for OSX/Darwin
git-svn: Fixes my() parameter list syntax error in pre-5.8 Perl
Git.pm: Use File::Temp->tempfile instead of ->new
t7501: always use test_cmp instead of diff
Start conforming code to "git subcmd" style part 2
diff: Help "less" hide ^M from the output
checkout: do not check out unmerged higher stages randomly
Conflicts:
Documentation/git.txt
Documentation/gitattributes.txt
Makefile
diff.c
t/t7201-co.sh
This is in preparation for allowing extended regular expression patterns.
Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This teaches "git merge-file" to honor merge.conflictstyle configuration
variable, whose value can be "merge" (default) or "diff3".
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This further enhances xdi_diff_outf() interface so that it takes two
common parameters: the callback function that processes one line at a
time, and a pointer to its application specific callback data structure.
xdi_diff_outf() creates its own "xdiff_emit_state" structure and stashes
these two away inside it, which is used by the lowest level output
function in the xdiff_outf() callchain, consume_one(), to call back to the
application layer. With this restructuring, we lift the requirement that
the caller supplied callback data structure embeds xdiff_emit_state
structure as its first member.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Continually xreallocing and freeing the remainder member of struct
xdiff_emit_state was a noticeable performance hit. Use a strbuf
instead.
This yields a decent performance improvement on "git blame" on certain
repositories. For example, before this commit:
$ time git blame -M -C -C -p --incremental server.c >/dev/null
101.52user 0.17system 1:41.73elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+39561minor)pagefaults 0swaps
With this commit:
$ time git blame -M -C -C -p --incremental server.c >/dev/null
80.38user 0.30system 1:20.81elapsed 99%CPU (0avgtext+0avgdata 0maxresident)k
0inputs+0outputs (0major+50979minor)pagefaults 0swaps
Signed-off-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
To prepare for the need to initialize and release resources for an
xdi_diff with the xdiff_outf output function, make a new function to
wrap this usage.
Old:
ecb.outf = xdiff_outf;
ecb.priv = &state;
...
xdi_diff(file_p, file_o, &xpp, &xecfg, &ecb);
New:
xdi_diff_outf(file_p, file_o, &state.xm, &xpp, &xecfg, &ecb);
Signed-off-by: Brian Downing <bdowning@lavos.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
* maint:
merge-file: handle empty files gracefully
merge-recursive: handle file mode changes
Minor wording changes in the keyboard descriptions in git-add --interactive.
git fetch: Take '-n' to mean '--no-tags'
quiltimport: fix misquoting of parsed -p<num> parameter
git-quiltimport: better parser to grok "enhanced" series files.
Earlier, it would error out while trying to read and/or writing them.
Now, calling merge-file with empty files is neither interesting nor
useful, but it is a bug that needed fixing.
Noticed by Clemens Buchacher.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
This change removes all obvious useless if-before-free tests.
E.g., it replaces code like this:
if (some_expression)
free (some_expression);
with the now-equivalent:
free (some_expression);
It is equivalent not just because POSIX has required free(NULL)
to work for a long time, but simply because it has worked for
so long that no reasonable porting target fails the test.
Here's some evidence from nearly 1.5 years ago:
http://www.winehq.org/pipermail/wine-patches/2006-October/031544.html
FYI, the change below was prepared by running the following:
git ls-files -z | xargs -0 \
perl -0x3b -pi -e \
's/\bif\s*\(\s*(\S+?)(?:\s*!=\s*NULL)?\s*\)\s+(free\s*\(\s*\1\s*\))/$2/s'
Note however, that it doesn't handle brace-enclosed blocks like
"if (x) { free (x); }". But that's ok, since there were none like
that in git sources.
Beware: if you do use the above snippet, note that it can
produce syntactically invalid C code. That happens when the
affected "if"-statement has a matching "else".
E.g., it would transform this
if (x)
free (x);
else
foo ();
into this:
free (x);
else
foo ();
There were none of those here, either.
If you're interested in automating detection of the useless
tests, you might like the useless-if-before-free script in gnulib:
[it *does* detect brace-enclosed free statements, and has a --name=S
option to make it detect free-like functions with different names]
http://git.sv.gnu.org/gitweb/?p=gnulib.git;a=blob;f=build-aux/useless-if-before-free
Addendum:
Remove one more (in imap-send.c), spotted by Jean-Luc Herren <jlh@gmx.ch>.
Signed-off-by: Jim Meyering <meyering@redhat.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The tar-ball and the git archive itself is fine, but yes, the diff from
2.6.23 to 2.6.24-rc6 is bad. It's the "trim_common_tail()" optimization
that has caused way too much pain.
Very interesting breakage. The patch was actually "correct" in a (rather
limited) technical sense, but the context at the end was missing because
while the trim_common_tail() code made sure to keep enough common context
to allow a valid diff to be generated, the diff machinery itself could
decide that it could generate the diff differently than the "obvious"
solution.
Thee sad fact is that the git optimization (which is very important for
"git blame", which needs no context), is only really valid for that one
case where we really don't need any context.
[jc: since this is shared with "git diff -U0" codepath, context recovery
to the end of line needs to be done even for zero context case.]
Signed-off-by: Junio C Hamano <gitster@pobox.com>
We need to be extra careful recovering the removed common section, so
that we do not break context nor the changed incomplete line (i.e. the
last line that does not end with LF).
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The recovered context lines were not LF terminated due to off-by-one
error, which also caused the outer loop to count the number of recovered
lines to terminate after running only once.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Inside xdiff library, the number of context lines is represented in
long, not int.
Noticed by Peter Baumann.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This implements earlier Linus's optimization to trim common lines at the
end before passing them down to low level xdiff interface for all of our
xdiff users.
We could later enhance this to also trim common leading lines, but that
would need tweaking the output function to add the number of lines
trimmed at the beginning to line numbers that appear in the hunk
headers.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This inserts a new function xdi_diff() that currently does not
do anything other than calling the underlying xdl_diff() to the
callchain of current callers of xdl_diff() function.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
