path: root/diffcore-break.c
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2010-05-07Add a macro DIFF_QUEUE_CLEAR.Bo Yang
Refactor the diff_queue_struct code, this macro help to reset the structure. Signed-off-by: Bo Yang <> Signed-off-by: Junio C Hamano <>
2009-11-16diffcore-break: save cnt_data for other phasesJeff King
The "break" phase works by counting changes between two blobs with the same path. We do this by splitting the file into chunks (or lines for text oriented files) and then keeping a count of chunk hashes. The "rename" phase counts changes between blobs at two different paths. However, it uses the exact same set of chunk hashes (which are immutable for a given sha1). The rename phase can therefore use the same hash data as break. Unfortunately, we were throwing this data away after computing it in the break phase. This patch instead attaches it to the filespec and lets it live through the rename phase, working under the assumption that most of the time that breaks are being computed, renames will be too. We only do this optimization for files which have actually been broken, as those ones will be candidates for rename detection (and it is a time-space tradeoff, so we don't want to waste space keeping useless data). Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2009-11-16diffcore-break: free filespec data as we goJeff King
As we look at each changed file and consider breaking it, we load the blob data and make a decision about whether to break, which is independent of any other blobs that might have changed. However, we keep the data in memory while we consider breaking all of the other files. Which means that both versions of every file you are diffing are in memory at the same time. This patch instead frees the blob data as we finish with each file pair, leading to much lower memory usage. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2009-03-08Remove unused function scope local variablesBenjamin Kramer
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 <> Signed-off-by: Junio C Hamano <>
2007-12-02rename: Break filepairs with different types.Junio C Hamano
When we consider if a path has been totally rewritten, we did not touch changes from symlinks to files or vice versa. But a change that modifies even the type of a blob surely should count as a complete rewrite. While we are at it, modernise diffcore-break to be aware of gitlinks (we do not want to touch them). Signed-off-by: Junio C Hamano <>
2007-10-21Fix diffcore-break total breakageLinus Torvalds
Ok, so on the kernel list, some people noticed that "git log --follow" doesn't work too well with some files in the x86 merge, because a lot of files got renamed in very special ways. In particular, there was a pattern of doing single commits with renames that looked basically like - rename "filename.h" -> "filename_64.h" - create new "filename.c" that includes "filename_32.h" or "filename_64.h" depending on whether we're 32-bit or 64-bit. which was preparatory for smushing the two trees together. Now, there's two issues here: - "filename.c" *remained*. Yes, it was a rename, but there was a new file created with the old name in the same commit. This was important, because we wanted each commit to compile properly, so that it was bisectable, so splitting the rename into one commit and the "create helper file" into another was *not* an option. So we need to break associations where the contents change too much. Fine. We have the -B flag for that. When we break things up, then the rename detection will be able to figure out whether there are better alternatives. - "git log --follow" didn't with with -B. Now, the second case was really simple: we use a different "diffopt" structure for the rename detection than the basic one (which we use for showing the diffs). So that second case is trivially fixed by a trivial one-liner that just copies the break_opt values from the "real" diffopts to the one used for rename following. So now "git log -B --follow" works fine: diff --git a/tree-diff.c b/tree-diff.c index 26bdbdd..7c261fd 100644 --- a/tree-diff.c +++ b/tree-diff.c @@ -319,6 +319,7 @@ static void try_to_follow_renames(struct tree_desc *t1, struct tree_desc *t2, co diff_opts.detect_rename = DIFF_DETECT_RENAME; diff_opts.output_format = DIFF_FORMAT_NO_OUTPUT; diff_opts.single_follow = opt->paths[0]; + diff_opts.break_opt = opt->break_opt; paths[0] = NULL; diff_tree_setup_paths(paths, &diff_opts); if (diff_setup_done(&diff_opts) < 0) however, the end result does *not* work. Because our diffcore-break.c logic is totally bogus! In particular: - it used to do if (base_size < MINIMUM_BREAK_SIZE) return 0; /* we do not break too small filepair */ which basically says "don't bother to break small files". But that "base_size" is the *smaller* of the two sizes, which means that if some large file was rewritten into one that just includes another file, we would look at the (small) result, and decide that it's smaller than the break size, so it cannot be worth it to break it up! Even if the other side was ten times bigger and looked *nothing* like the samell file! That's clearly bogus. I replaced "base_size" with "max_size", so that we compare the *bigger* of the filepair with the break size. - It calculated a "merge_score", which was the score needed to merge it back together if nothing else wanted it. But even if it was *so* different that we would never want to merge it back, we wouldn't consider it a break! That makes no sense. So I added if (*merge_score_p > break_score) return 1; to make it clear that if we wouldn't want to merge it at the end, it was *definitely* a break. - It compared the whole "extent of damage", counting all inserts and deletes, but it based this score on the "base_size", and generated the damage score with delta_size = src_removed + literal_added; damage_score = delta_size * MAX_SCORE / base_size; but that makes no sense either, since quite often, this will result in a number that is *bigger* than MAX_SCORE! Why? Because base_size is (again) the smaller of the two files we compare, and when you start out from a small file and add a lot (or start out from a large file and remove a lot), the base_size is going to be much smaller than the damage! Again, the fix was to replace "base_size" with "max_size", at which point the damage actually becomes a sane percentage of the whole. With these changes in place, not only does "git log -B --follow" work for the case that triggered this in the first place, ie now git log -B --follow arch/x86/kernel/ actually gives reasonable results. But I also wanted to verify it in general, by doing a full-history git log --stat -B -C on my kernel tree with the old code and the new code. There's some tweaking to be done, but generally, the new code generates much better results wrt breaking up files (and then finding better rename candidates). Here's a few examples of the "--stat" output: - This: include/asm-x86/Kbuild | 2 - include/asm-x86/debugreg.h | 79 +++++++++++++++++++++++++++++++++++------ include/asm-x86/debugreg_32.h | 64 --------------------------------- include/asm-x86/debugreg_64.h | 65 --------------------------------- 4 files changed, 68 insertions(+), 142 deletions(-) Becomes: include/asm-x86/Kbuild | 2 - include/asm-x86/{debugreg_64.h => debugreg.h} | 9 +++- include/asm-x86/debugreg_32.h | 64 ------------------------- 3 files changed, 7 insertions(+), 68 deletions(-) - This: include/asm-x86/bug.h | 41 +++++++++++++++++++++++++++++++++++++++-- include/asm-x86/bug_32.h | 37 ------------------------------------- include/asm-x86/bug_64.h | 34 ---------------------------------- 3 files changed, 39 insertions(+), 73 deletions(-) Becomes include/asm-x86/{bug_64.h => bug.h} | 20 +++++++++++++----- include/asm-x86/bug_32.h | 37 ----------------------------------- 2 files changed, 14 insertions(+), 43 deletions(-) Now, in some other cases, it does actually turn a rename into a real "delete+create" pair, and then the diff is usually bigger, so truth in advertizing: it doesn't always generate a nicer diff. But for what -B was meant for, I think this is a big improvement, and I suspect those cases where it generates a bigger diff are tweakable. So I think this diff fixes a real bug, but we might still want to tweak the default values and perhaps the exact rules for when a break happens. Signed-off-by: Linus Torvalds <> Signed-off-by: Shawn O. Pearce <>
2007-07-01diffcore_count_changes: pass diffcore_filespecJunio C Hamano
We may want to use richer information on the data we are dealing with in this function, so instead of passing a buffer address and length, just pass the diffcore_filespec structure. Existing callers always call this function with parameters taken from a filespec anyway, so there is no functionality changes. Signed-off-by: Junio C Hamano <>
2007-03-07Cast 64 bit off_t to 32 bit size_tShawn O. Pearce
Some systems have sizeof(off_t) == 8 while sizeof(size_t) == 4. This implies that we are able to access and work on files whose maximum length is around 2^63-1 bytes, but we can only malloc or mmap somewhat less than 2^32-1 bytes of memory. On such a system an implicit conversion of off_t to size_t can cause the size_t to wrap, resulting in unexpected and exciting behavior. Right now we are working around all gcc warnings generated by the -Wshorten-64-to-32 option by passing the off_t through xsize_t(). In the future we should make xsize_t on such problematic platforms detect the wrapping and die if such a file is accessed. Signed-off-by: Shawn O. Pearce <> Signed-off-by: Junio C Hamano <>
2006-08-17Do not use memcmp(sha1_1, sha1_2, 20) with hardcoded length.David Rientjes
Introduces global inline: hashcmp(const unsigned char *sha1, const unsigned char *sha2) Uses memcmp for comparison and returns the result based on the length of the hash name (a future runtime decision). Acked-by: Alex Riesen <> Signed-off-by: David Rientjes <> Signed-off-by: Junio C Hamano <>
2006-03-12diffcore-rename: somewhat optimized.Junio C Hamano
This changes diffcore-rename to reuse statistics information gathered during similarity estimation, and updates the hashtable implementation used to keep track of the statistics to be denser. This seems to give better performance. Signed-off-by: Junio C Hamano <>
2006-03-04diffcore-break: similarity estimator fix.Junio C Hamano
This is a companion patch to the previous fix to diffcore-rename. The merging-back process should use a logic similar to what is used there. Signed-off-by: Junio C Hamano <>
2006-03-01diffcore-rename: split out the delta counting code.Junio C Hamano
This is to rework diffcore break/rename/copy detection code so that it does not affected when deltifier code gets improved. Signed-off-by: Junio C Hamano <>
2006-03-01diffcore-break: micro-optimize by avoiding delta between identical files.Junio C Hamano
We did not check if we have the same file on both sides when computing break score. This is usually not a problem, but if the user said --find-copies-harde with -B, we ended up trying a delta between the same data even when we know the SHA1 hash of both sides match. Signed-off-by: Junio C Hamano <>
2005-12-13diffcore-break: do not break too small filepair.Junio C Hamano
Somehow we checked only one side and not the other. By checking the filesize upfront, we can bypass generating delta unnecessarily. Signed-off-by: Junio C Hamano <>
2005-12-12diffcore-break.c: check diff_delta() return value.Junio C Hamano
This bug caused Darrin Thompson to notice that our deltifier was half broken and punting on an empty blob. Signed-off-by: Junio C Hamano <>
2005-09-14Revert "[PATCH] plug memory leak in diff.c::diff_free_filepair()"Junio C Hamano
This reverts 068eac91ce04b9aca163acb1927c3878c45d1a07 commit.
2005-08-14[PATCH] plug memory leak in diff.c::diff_free_filepair()Yasushi SHOJI
When I run git-diff-tree on big change, it seems the command eats so much memory. so I just put git under valgrind to see what's going on. diff_free_filespec_data() doesn't free diff_filespec itself. [jc: I ended up doing things slightly differently from Yasushi's patch. The original idea was to use free_filespec_data() only to free the data portion and keep useing the filespec itself, but no existing code seems to do things that way, so I just yanked that part out.] Signed-off-by: Yasushi SHOJI <> Signed-off-by: Junio C Hamano <>
2005-06-29[PATCH] Fixlets on top of Nico's clean-up.Junio C Hamano
If we prefer 0 as maxsize for diff_delta() to say "unlimited", let's be consistent about it. This patch also fixes type mismatch in a call to get_delta_hdr_size() from packed_delta_info(). Signed-off-by: Junio C Hamano <> Signed-off-by: Linus Torvalds <>
2005-06-26Add a "max_size" parameter to diff_delta()Linus Torvalds
Anything that generates a delta to see if two objects are close usually isn't interested in the delta ends up being bigger than some specified size, and this allows us to stop delta generation early when that happens.
2005-06-20[PATCH] Rework -B output.Junio C Hamano
Patch for a completely rewritten file detected by the -B flag was shown as a pair of creation followed by deletion in earlier versions. This was an misguided attempt to make reviewing such a complete rewrite easier, and unnecessarily ended up confusing git-apply. Instead, show the entire contents of old version prefixed with '-', followed by the entire contents of new version prefixed with '+'. This gives the same easy-to-review for human consumer while keeping it a single, regular modification patch for machine consumption, something that even GNU patch can grok. Signed-off-by: Junio C Hamano <> Signed-off-by: Linus Torvalds <>
2005-06-05[PATCH] diffcore-break.c: various fixes.Junio C Hamano
This fixes three bugs in the -B heuristics. - Although it was advertised that the initial break criteria used was the same as what diffcore-rename uses, it was using something different. Instead of using smaller of src and dst size to compare with "edit" size, (insertion and deletion), it was using larger of src and dst, unlike the rename/copy detection logic. This caused the parameter to -B to mean something different from the one to -M and -C. To compensate for this change, the default break score is also changed to match that of the default for rename/copy. - The code would have crashed with division by zero when trying to break an originally empty file. - Contrary to what the comment said, the algorithm was breaking small files, only to later merge them together. Signed-off-by: Junio C Hamano <> Signed-off-by: Linus Torvalds <>
2005-06-03[PATCH] diff: Update -B heuristics.Junio C Hamano
As Linus pointed out on the mailing list discussion, -B should break a files that has many inserts even if it still keeps enough of the original contents, so that the broken pieces can later be matched with other files by -M or -C. However, if such a broken pair does not get picked up by -M or -C, we would want to apply different criteria; namely, regardless of the amount of new material in the result, the determination of "rewrite" should be done by looking at the amount of original material still left in the result. If you still have the original 97 lines from a 100-line document, it does not matter if you add your own 13 lines to make a 110-line document, or if you add 903 lines to make a 1000-line document. It is not a rewrite but an in-place edit. On the other hand, if you did lose 97 lines from the original, it does not matter if you added 27 lines to make a 30-line document or if you added 997 lines to make a 1000-line document. You did a complete rewrite in either case. This patch introduces a post-processing phase that runs after diffcore-rename matches up broken pairs diffcore-break creates. The purpose of this post-processing is to pick up these broken pieces and merge them back into in-place modifications. For this, the score parameter -B option takes is changed into a pair of numbers, and it takes "-B99/80" format when fully spelled out. The first number is the minimum amount of "edit" (same definition as what diffcore-rename uses, which is "sum of deletion and insertion") that a modification needs to have to be broken, and the second number is the minimum amount of "delete" a surviving broken pair must have to avoid being merged back together. It can be abbreviated to "-B" to use default for both, "-B9" or "-B9/" to use 90% for "edit" but default (80%) for merge avoidance, or "-B/75" to use default (99%) "edit" and 75% for merge avoidance. Signed-off-by: Junio C Hamano <> Signed-off-by: Linus Torvalds <>
2005-06-03[PATCH] Tweak count-delta interfaceJunio C Hamano
Make it return copied source and insertion separately, so that later implementation of heuristics can use them more flexibly. This does not change the heuristics implemented in diffcore-rename nor diffcore-break in any way. Signed-off-by: Junio C Hamano <> Signed-off-by: Linus Torvalds <>
2005-05-30[PATCH] Add -B flag to diff-* brothers.Junio C Hamano
A new diffcore transformation, diffcore-break.c, is introduced. When the -B flag is given, a patch that represents a complete rewrite is broken into a deletion followed by a creation. This makes it easier to review such a complete rewrite patch. The -B flag takes the same syntax as the -M and -C flags to specify the minimum amount of non-source material the resulting file needs to have to be considered a complete rewrite, and defaults to 99% if not specified. As the new test demonstrates, if a file is a complete rewrite, it is broken into a delete/create pair, which can further be subjected to the usual rename detection if -M or -C is used. For example, if file0 gets completely rewritten to make it as if it were rather based on file1 which itself disappeared, the following happens: The original change looks like this: file0 --> file0' (quite different from file0) file1 --> /dev/null After diffcore-break runs, it would become this: file0 --> /dev/null /dev/null --> file0' file1 --> /dev/null Then diffcore-rename matches them up: file1 --> file0' The internal score values are finer grained now. Earlier maximum of 10000 has been raised to 60000; there is no user visible changes but there is no reason to waste available bits. Signed-off-by: Junio C Hamano <> Signed-off-by: Linus Torvalds <>