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"zdiff3" is identical to ordinary diff3 except that it allows compaction
of common lines on the two sides of history at the beginning or end of
the conflict hunk. For example, the following diff3 conflict:
1
2
3
4
<<<<<<
A
B
C
D
E
||||||
5
6
======
A
X
C
Y
E
>>>>>>
7
8
9
has common lines 'A', 'C', and 'E' on the two sides. With zdiff3, one
would instead get the following conflict:
1
2
3
4
A
<<<<<<
B
C
D
||||||
5
6
======
X
C
Y
>>>>>>
E
7
8
9
Note that the common lines, 'A', and 'E' were moved outside the
conflict. Unlike with the two-way conflicts from the 'merge'
conflictStyle, the zdiff3 conflict is NOT split into multiple conflict
regions to allow the common 'C' lines to be shown outside a conflict,
because zdiff3 shows the base version too and the base version cannot be
reasonably split.
Note also that the removing of lines common to the two sides might make
the remaining text inside the conflict region match the base text inside
the conflict region (for example, if the diff3 conflict had '5 6 E' on
the right side of the conflict, then the common line 'E' would be moved
outside and both the base and right side's remaining conflict text would
be the lines '5' and '6'). This has the potential to surprise users and
make them think there should not have been a conflict, but there
definitely was a conflict and it should remain.
Based-on-patch-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
Co-authored-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Phillip Wood <phillip.wood123@gmail.com>
Signed-off-by: Elijah Newren <newren@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The mailing address for the FSF has changed over the years. Rather than
updating the address across all files, refer readers to gnu.org, as the
GNU GPL documentation now suggests for license notices. The mailing
address is retained in the full license files (COPYING and LGPL-2.1).
The old address is still present in t/diff-lib/COPYING. This is
intentional, as the file is used in tests and the contents are not
expected to change.
Signed-off-by: Todd Zullinger <tmz@pobox.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* ps/plug-xdl-merge-leak:
xdiff/xmerge: fix memory leak in xdl_merge
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When building the script for the second file that is to be merged
we have already allocated memory for data structures related to
the first file. When we encounter an error in building the second
script we only free allocated memory related to the second file
before erroring out.
Fix this memory leak by also releasing allocated memory related
to the first file.
Helped-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In the previous patch, we made sure that the conflict markers themselves
match the end-of-line style of the input files. However, this still left
out the conflicting text itself: if it lacks a trailing newline, we
add one, and should add a carriage return when appropriate, too.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When merging files with CR/LF line endings, the conflict markers should
match those, lest the output file has mixed line endings.
This is particularly of interest on Windows, where some editors get
*really* confused by mixed line endings.
The original version of this patch by Beat Bolli respected core.eol, and
a subsequent improvement by this developer also respected gitattributes.
This approach was suboptimal, though: `git merge-file` was invented as a
drop-in replacement for GNU merge and as such has no problem operating
outside of any repository at all!
Another problem with the original approach was pointed out by Junio
Hamano: legacy repositories might have their text files committed using
CR/LF line endings (and core.eol and the gitattributes would give us a
false impression there). Therefore, the much superior approach is to
simply match the context's line endings, if any.
We actually do not have to look at the *entire* context at all: if the
files are all LF-only, or if they all have CR/LF line endings, it is
sufficient to look at just a *single* line to match that style. And if
the line endings are mixed anyway, it is *still* okay to imitate just a
single line's eol: we will just add to the pile of mixed line endings,
and there is nothing we can do about that.
So what we do is: we look at the line preceding the conflict, falling
back to the line preceding that in case it was the last line and had no
line ending, falling back to the first line, first in the first
post-image, then the second post-image, and finally the pre-image.
If we find consistent CR/LF (or undecided) end-of-line style, we match
that, otherwise we use LF-only line endings for the conflict markers.
Note that while it is true that there have to be at least two lines we
can look at (otherwise there would be no conflict), the same is not true
for line *endings*: the three files in question could all consist of a
single line without any line ending, each. In this case we fall back to
using LF-only.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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If 'current-file' does not contain LF at EOF, and change between
'base-file' and 'other-file' does not change any line close to EOF, the
3-way merge should not add LF to EOF. This is what 'diff3 -m' does, and
seems to be a reasonable expectation.
The change which introduced the behavior is cd1d61c44f. It always calls
function xdl_recs_copy() for sides with add_nl == 1. In fact, it looks
like the only case when this is needed is when 2 files are being
union-merged, and they do not have LF at EOF (strictly speaking, the
first of them).
Add tests:
* "merge without conflict (missing LF at EOF, away from change in the
other file)" and "merge does not add LF away of change", to demonstrate
the changed behavior.
* "conflict at EOF without LF resolved by --union", to verify that the
union-merge at the end inerts newline between versions.
* some more tests which I felt like not covering the functionality well
Signed-off-by: Max Kirillov <max@max630.net>
Acked-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The ctype functions isspace(), isalnum(), et al take an integer
argument representing an unsigned character, or -1 for EOF. On
platforms with a signed char, it is unsafe to pass a char to them
without casting it to unsigned char first.
Most of git is already shielded against this by the ctype
implementation in git-compat-util.h, but xdiff, which uses libc
ctype.h, ought to be fixed.
Noticed-by: der Mouse <mouse@Rodents-Montreal.ORG>
Reported-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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memset() is heavily optimized, and resulting assembler code
is about 150 lines less for that file.
Signed-off-by: Alexey Mahotkin <squadette@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The labels for the three participants in a potential conflict are all
optional arguments for the xdiff merge routine; if they are NULL, then
xdl_merge() can cope by omitting the labels from its output. Move
them to the xmparam structure to allow new callers to save some
keystrokes where they are not needed.
This also has the virtue of making the xdiff merge interface more
similar to merge_trees, which might make it easier to learn.
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The ‘git checkout --conflict=diff3’ command can be used to
present conflicts hunks including text from the common ancestor:
<<<<<<< ours
ourside
|||||||
original
=======
theirside
>>>>>>> theirs
The added information is helpful for resolving merges by hand, and
merge tools can usually grok it because it is very similar to the
output from diff3 -m.
A subtle change can help more tools to understand the output. ‘diff3’
includes the name of the merge base on the ||||||| line of the output,
and some tools misparse the conflict hunks without it. Add a new
xmp->ancestor parameter to xdl_merge() for use with conflict style
XDL_MERGE_DIFF3 as a label on the ||||||| line for any conflict hunks.
If xmp->ancestor is NULL, the output format is unchanged. Thus, this
change only provides unexposed plumbing for the new feature; it does
not affect the outward behavior of git.
Requested-by: Stefan Monnier <monnier@iro.umontreal.ca>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Acked-by: Bert Wesarg <Bert.Wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Include the merge level, favor, and style flags into the xmparam_t struct.
This removes the bit twiddling with these three values into the one flags
parameter.
Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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The current union merge driver is implemented as an post process. But the
xdl_merge code is quite capable to produce the result by itself. Therefore
move it there.
Signed-off-by: Bert Wesarg <bert.wesarg@googlemail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* jc/conflict-marker-size:
rerere: honor conflict-marker-size attribute
rerere: prepare for customizable conflict marker length
conflict-marker-size: new attribute
rerere: use ll_merge() instead of using xdl_merge()
merge-tree: use ll_merge() not xdl_merge()
xdl_merge(): allow passing down marker_size in xmparam_t
xdl_merge(): introduce xmparam_t for merge specific parameters
git_attr(): fix function signature
Conflicts:
builtin-merge-file.c
ll-merge.c
xdiff/xdiff.h
xdiff/xmerge.c
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This allows the callers of xdl_merge() to pass marker_size (defaults to 7)
in xmparam_t argument, to use conflict markers of non-default length.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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So far we have only needed to be able to pass an option that is generic to
xdiff family of functions to this function. Extend the interface so that
we can give it merge specific parameters.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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Sometimes people want their conflicting merges autoresolved by
favouring upstream changes. The standard answer they are given is
to run "git diff --name-only | xargs git checkout MERGE_HEAD --" in
such a case. This is to accept automerge results for the paths that
are fully resolved automatically, while taking their version of the
file in full for paths that have conflicts.
This is problematic on two counts.
One is that this is not exactly what these people want. It discards
all changes they did on their branch for any paths that conflicted.
They usually want to salvage as much automerge result as possible in
a conflicted file, and want to take the upstream change only in the
conflicted part.
This patch teaches two new modes of operation to the lowest-lever
merge machinery, xdl_merge(). Instead of leaving the conflicted
lines from both sides enclosed in <<<, ===, and >>> markers, the
conflicts are resolved favouring our side or their side of changes.
A larger problem is that this tends to encourage a bad workflow by
allowing people to record such a mixed up half-merged result as a
full commit without auditing. This commit does not tackle this
issue at all. In git, we usually give long enough rope to users
with strange wishes as long as the risky features are not enabled by
default, and this is such a risky feature.
Signed-off-by: Avery Pennarun <apenwarr@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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* cb/maint-1.6.0-xdl-merge-fix:
Change xdl_merge to generate output even for null merges
t6023: merge-file fails to output anything for a degenerate merge
Conflicts:
xdiff/xmerge.c
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xdl_merge used to have a check to ensure that there was at least
some change in one or other side being merged but this suppressed
output for the degenerate case when base, local and remote
contents were all identical.
Removing this check enables correct output in the degenerate case
and xdl_free_script handles freeing NULL scripts so there is no
need to have the check for these calls.
Signed-off-by: Charles Bailey <charles@hashpling.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When showing a conflicting merge result, and "--diff3 -m" style is asked
for, this patch makes sure that the merge reduction level does not exceed
XDL_MERGE_EAGER. This is because "diff3 -m" style output would not make
sense for anything more aggressive than XDL_MERGE_EAGER, because of the
way how the merge reduction works.
"git merge-file" no longer has to force MERGE_EAGER when "--diff3" is
asked for because of this change.
Suppose a common ancestor (shared preimage) is modified to postimage #1
and #2 (each letter represents one line):
#####
postimage#1: 1234ABCDE789
| /
| /
preimage: 123456789
| \
postimage#2: 1234AXYE789
####
XDL_MERGE_MINIMAL and XDL_MERGE_EAGER would:
(1) find the s/56/ABCDE/ done on one side and s/56/AXYE/ done on the
other side,
(2) notice that they touch an overlapping area, and
(3) mark it as a conflict, "ABCDE vs AXYE".
The difference between the two algorithms is that EAGER drops the hunk
altogether if the postimages match (i.e. both sides modified the same
way), while MINIMAL keeps it. There is no other operation performed to
the hunk. As the result, lines marked with "#" in the above picure will
be in the RCS merge style output like this (letters <, = and > represent
conflict marker lines):
output: 1234<ABCDE=AXYE>789 ; with MINIMAL/EAGER
The part from the preimage that corresponds to these conflicting changes
is "56", which is what "diff3 -m" style output adds to it:
output: 1234<ABCDE|56=AXYE>789 ; in "diff3 -m" style
Now, XDL_MERGE_ZEALOUS looks at the differences between the changes two
postimages made in order to reduce the number of lines in the conflicting
regions. It notices that both sides start their new contents with "A",
and excludes it from the output (it also excludes "E" for the same
reason). The conflict that used to be "ABCDE vs AXYE" is now "BCD vs XY":
output: 1234A<BCD=XY>E789 ; with ZEALOUS
There could even be matching parts between two postimages in the middle.
Instead of one side rewriting the shared "56" to "ABCDE" and the other
side to "AXYE", imagine the case where the postimages are "ABCDE" and
"AXCYE", in which case instead of having one conflicted hunk "BCD vs XY",
you would have two conflicting hunks "B vs X" and "D vs Y".
In either case, once you reduce "ABCDE vs AXYE" to "BCD vs XY" (or "ABCDE
vs AXCYE" to "B vs X" and "D vs Y"), there is no part from the preimage
that corresponds to the conflicting change made in both postimages
anymore. In other words, conflict reduced by ZEALOUS algorithm cannot be
expressed in "diff3 -m" style. Representing the last illustration like
this is misleading to say the least:
output: 1234A<BCD|56=XY>E789 ; broken "diff3 -m" style
because the preimage was not ...4A56E... to begin with. "A" and "E" are
common only between the postimages.
Even worse, once a single conflicting hunk is split into multiple ones
(recall the example of breaking "ABCDE vs AXCYE" to "B vs X" and "D vs
Y"), there is no sane way to distribute the preimage text across split
conflicting hunks.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This replaces hardcoded magic constants with symbolic ones for
readability, and swaps one if/else blocks to better match the
order in which 0/1/2 variables are handled to nearby codepath.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When showing conflicting merges, we traditionally followed RCS's merge
output format. The output shows:
<<<<<<<
postimage from one side;
=======
postimage of the other side; and
>>>>>>>
Some poeple find it easier to be able to understand what is going on when
they can view the common ancestor's version, which is used by "diff3 -m",
which shows:
<<<<<<<
postimage from one side;
|||||||
shared preimage;
=======
postimage of the other side; and
>>>>>>>
This is an initial step to bring that as an optional feature to git.
Only "git merge-file" has been converted, with "--diff3" option.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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This simply moves code around to make a separate function that prepares
a single conflicted hunk with markers into the buffer.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When a merge conflicts, there are often common lines that are not really
common, such as empty lines or lines containing a single curly bracket.
With XDL_MERGE_ZEALOUS_ALNUM, we use the following heuristics: when a
hunk does not contain any letters or digits, it is treated as conflicting.
In other words, a conflict which used to look like this:
<<<<<<<
a = 1;
=======
output();
>>>>>>>
}
}
}
<<<<<<<
output();
=======
b = 1;
>>>>>>>
will look like this with ZEALOUS_ALNUM:
<<<<<<<
a = 1;
}
}
}
output();
=======
output();
}
}
}
b = 1;
>>>>>>>
To demonstrate this, git-merge-file has been switched from
XDL_MERGE_ZEALOUS to XDL_MERGE_ZEALOUS_ALNUM.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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When a merge conflicts, there are often less than three common lines
between two conflicting regions.
Since a conflict takes up as many lines as are conflicting, plus three
lines for the commit markers, the output will be shorter (and thus,
simpler) in this case, if the common lines will be merged into the
conflicting regions.
This patch merges up to three common lines into the conflicts.
For example, what looked like this before this patch:
<<<<<<<
if (a == 1)
=======
if (a != 0)
>>>>>>>
{
int i;
<<<<<<<
a = 0;
=======
a = !a;
>>>>>>>
will now look like this:
<<<<<<<
if (a == 1)
{
int i;
a = 0;
=======
if (a != 0)
{
int i;
a = !a;
>>>>>>>
Suggested Linus (based on ideas by "Voltage Spike" -- if that name is
real, it is mighty cool).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
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In very obscure cases, a merge can hit an unexpected code path (where the
original code went as far as saying that this was a bug). This failing
merge was noticed by Alexandre Juillard.
The problem is that the original file contains something like this:
-- snip --
two non-empty lines
before two empty lines
after two empty lines
-- snap --
and this snippet is reduced to _one_ empty line in _both_ new files.
However, it is ambiguous as to which hunk takes the empty line: the first
or the second one?
Indeed in Alexandre's example files, the xdiff algorithm attributes the
empty line to the first hunk in one case, and to the second hunk in the
other case.
(Trimming down the example files _changes_ that behaviour!)
Thus, the call to xdl_merge_cmp_lines() has no chance to realize that the
change is actually identical in both new files. Therefore,
xdl_refine_conflicts() finds an empty diff script, which was not expected
there, because (the original author of xdl_merge() thought)
xdl_merge_cmp_lines() would catch that case earlier.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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The function xdl_refine_conflicts() tries to break down huge
conflicts by doing a diff on the conflicting regions. However,
this does not make sense when one side is empty.
Worse, when one side is not only empty, but after EOF, the code
accessed unmapped memory.
Noticed by Luben Tuikov, Shawn Pearce and Alexandre Julliard, the
latter providing a test case.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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Suppose you have changes in new1 to the original lines 10-20,
and changes in new2 to the original lines 15-25, then the
changes to 10-25 conflict. But it is possible that the next
changes in new1 still overlap with this change to new2.
So, in the next iteration we have to look at the same change
to new2 again.
The old code tried to be a bit too clever. The new code is
shorter and more to the point: do not fiddle with the ranges
at all.
Also, xdl_append_merge() tries harder to combine conflicts.
This is necessary, because with the above simplification,
some conflicts would not be recognized as conflicts otherwise:
In the above scenario, it is possible that there is no other
change to new1. Absent the combine logic, the change in new2
would be recorded _again_, but as a non-conflict.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
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If one side's block (of changed lines) ends later than the other
side's block, the former should be tested against the next block
of the other side, not vice versa.
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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The line range is i1 .. (i1 + chg1 - 1), not i1 .. (i1 + chg1).
Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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The callers would want to know if the resulting merge is clean;
do not discard that information away after calling xdl_do_merge().
Signed-off-by: Junio C Hamano <junkio@cox.net>
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This new function implements the functionality of RCS merge, but
in-memory. It returns < 0 on error, otherwise the number of conflicts.
Finding the conflicting lines can be a very expensive task. You can
control the eagerness of this algorithm:
- a level value of 0 means that all overlapping changes are treated
as conflicts,
- a value of 1 means that if the overlapping changes are identical,
it is not treated as a conflict.
- If you set level to 2, overlapping changes will be analyzed, so that
almost identical changes will not result in huge conflicts. Rather,
only the conflicting lines will be shown inside conflict markers.
With each increasing level, the algorithm gets slower, but more accurate.
Note that the code for level 2 depends on the simple definition of
mmfile_t specific to git, and therefore it will be harder to port that
to LibXDiff.
Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>
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Phillip Wood
Todd Zullinger
Junio C Hamano
Patrick Steinhardt
Johannes Schindelin
Max Kirillov
Jonathan Nieder
Alexey Mahotkin
Bert Wesarg
Charles Bailey
Junio C Hamano