src/diff_generate.c


Log

Author Commit Date CI Message
Edward Thomson 3be73011 2018-06-11T18:26:22 Merge pull request #4436 from pks-t/pks/packfile-stream-free pack: rename `git_packfile_stream_free`
Patrick Steinhardt ecf4f33a 2018-02-08T11:14:48 Convert usage of `git_buf_free` to new `git_buf_dispose`
David Turner 5a7d454b 2018-06-04T12:56:08 Fix stash save bug with fast path index check If the index contains stat data for a modified file, and the file is not racily dirty, and there exists an untracked working tree directory alphabetically after that file, and there are no other changes to the repo, then git_stash_save would fail. It would confuse the untracked working tree directory for the modified file, because they have the same sha: zero. The wt directory has a sha of zero because it's a directory, and the file would have a zero sha because we wouldn't read the file -- we would just know that it doesn't match the index. To fix this confusion, we simply check mode as well as SHA.
Patrick Steinhardt d8896bda 2018-01-03T16:07:36 diff_generate: avoid excessive stats of .gitattribute files When generating a diff between two trees, for each file that is to be diffed we have to determine whether it shall be treated as text or as binary files. While git has heuristics to determine which kind of diff to generate, users can also that default behaviour by setting or unsetting the 'diff' attribute for specific files. Because of that, we have to query gitattributes in order to determine how to diff the current files. Instead of hitting the '.gitattributes' file every time we need to query an attribute, which can get expensive especially on networked file systems, we try to cache them instead. This works perfectly fine for every '.gitattributes' file that is found, but we hit cache invalidation problems when we determine that an attribuse file is _not_ existing. We do create an entry in the cache for missing '.gitattributes' files, but as soon as we hit that file again we invalidate it and stat it again to see if it has now appeared. In the case of diffing large trees with each other, this behaviour is very suboptimal. For each pair of files that is to be diffed, we will repeatedly query every directory component leading towards their respective location for an attributes file. This leads to thousands or even hundreds of thousands of wasted syscalls. The attributes cache already has a mechanism to help in that scenario in form of the `git_attr_session`. As long as the same attributes session is still active, we will not try to re-query the gitmodules files at all but simply retain our currently cached results. To fix our problem, we can create a session at the top-most level, which is the initialization of the `git_diff` structure, and use it in order to look up the correct diff driver. As the `git_diff` structure is used to generate patches for multiple files at once, this neatly solves our problem by retaining the session until patches for all files have been generated. The fix has been tested with linux.git by calling `git_diff_tree_to_tree` and `git_diff_to_buf` with v4.10^{tree} and v4.14^{tree}. | time | .gitattributes stats without fix | 33.201s | 844614 with fix | 30.327s | 4441 While execution only improved by roughly 10%, the stat(3) syscalls for .gitattributes files decreased by 99.5%. The benchmarks were quite simple with best-of-three timings on Linux ext4 systems. One can assume that for network based file systems the performance gain will be a lot larger due to a much higher latency.
Patrick Steinhardt 5ca3f115 2017-11-30T15:12:48 diff_generate: fix unsetting diff flags The macro `DIFF_FLAG_SET` can be used to set or unset a flag by modifying the diff's bitmask. While the case of setting the flag is handled correctly, the case of unsetting the flag was not. Instead of inverting the flags, we are inverting the value which is used to decide whether we want to set or unset the bits. The value being used here is a simple `bool` which is `false`. As that is being uplifted to `int` when getting the bitwise-complement, we will end up retaining all bits inside of the bitmask. As that's only ever used to set `GIT_DIFF_IGNORE_CASE`, we were actually always ignoring case for generated diffs. Fix that by instead getting the bitwise-complement of `FLAG`, not `VAL`.
Patrick Steinhardt 585b5dac 2017-11-18T15:43:11 refcount: make refcounting conform to aliasing rules Strict aliasing rules dictate that for most data types, you are not allowed to cast them to another data type and then access the casted pointers. While this works just fine for most compilers, technically we end up in undefined behaviour when we hurt that rule. Our current refcounting code makes heavy use of casting and thus violates that rule. While we didn't have any problems with that code, Travis started spitting out a lot of warnings due to a change in their toolchain. In the refcounting case, the code is also easy to fix: as all refcounting-statements are actually macros, we can just access the `rc` field directly instead of casting. There are two outliers in our code where that doesn't work. Both the `git_diff` and `git_patch` structures have specializations for generated and parsed diffs/patches, which directly inherit from them. Because of that, the refcounting code is only part of the base structure and not of the children themselves. We can help that by instead passing their base into `GIT_REFCOUNT_INC`, though.
Patrick Steinhardt 0c7f49dd 2017-06-30T13:39:01 Make sure to always include "common.h" first Next to including several files, our "common.h" header also declares various macros which are then used throughout the project. As such, we have to make sure to always include this file first in all implementation files. Otherwise, we might encounter problems or even silent behavioural differences due to macros or defines not being defined as they should be. So in fact, our header and implementation files should make sure to always include "common.h" first. This commit does so by establishing a common include pattern. Header files inside of "src" will now always include "common.h" as its first other file, separated by a newline from all the other includes to make it stand out as special. There are two cases for the implementation files. If they do have a matching header file, they will always include this one first, leading to "common.h" being transitively included as first file. If they do not have a matching header file, they instead include "common.h" as first file themselves. This fixes the outlined problems and will become our standard practice for header and source files inside of the "src/" from now on.
Edward Thomson 909d5494 2016-12-29T12:25:15 giterr_set: consistent error messages Error messages should be sentence fragments, and therefore: 1. Should not begin with a capital letter, 2. Should not conclude with punctuation, and 3. Should not end a sentence and begin a new one
Edward Thomson b859faa6 2016-08-23T23:38:39 Teach `git_patch_from_diff` about parsed diffs Ensure that `git_patch_from_diff` can return the patch for parsed diffs, not just generate a patch for a generated diff.
Edward Thomson 7166bb16 2016-04-25T00:35:48 introduce `git_diff_from_buffer` to parse diffs Parse diff files into a `git_diff` structure.
Edward Thomson 9be638ec 2016-04-19T15:12:18 git_diff_generated: abstract generated diffs