git/diff.h, branch v2.15.2

diff: define block by number of alphanumeric chars

2017-08-16T18:44:00Z

The existing behavior of diff --color-moved=zebra does not define the minimum size of a block at all, instead relying on a heuristic applied later to filter out sets of adjacent moved lines that are shorter than 3 lines long. This can be confusing, because a block could thus be colored as moved at the source but not at the destination (or vice versa), depending on its neighbors. Instead, teach diff that the minimum size of a block is 20 alphanumeric characters, the same heuristic used by "git blame". This allows diff to still exclude uninteresting lines appearing on their own (such as those solely consisting of one or a few closing braces), as was the intention of the adjacent-moved-line heuristic. This requires a change in some tests in that some of their lines are no longer considered to be part of a block, because they are too short. Signed-off-by: Jonathan Tan Signed-off-by: Junio C Hamano

diff.c: add dimming to moved line detection

2017-06-30T20:59:42Z

Any lines inside a moved block of code are not interesting. Boundaries of blocks are only interesting if they are next to another block of moved code. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

diff.c: color moved lines differently, plain mode

2017-06-30T20:59:42Z

Add the 'plain' mode for move detection of code. This omits the checking for adjacent blocks, so it is not as useful. If you have a lot of the same blocks moved in the same patch, the 'Zebra' would end up slow as it is O(n^2) (n is number of same blocks). So this may be useful there and is generally easy to add. Instead be very literal at the move detection, do not skip over short blocks here. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

diff.c: color moved lines differently

2017-06-30T20:59:42Z

When a patch consists mostly of moving blocks of code around, it can be quite tedious to ensure that the blocks are moved verbatim, and not undesirably modified in the move. To that end, color blocks that are moved within the same patch differently. For example (OM, del, add, and NM are different colors): [OM] -void sensitive_stuff(void) [OM] -{ [OM] - if (!is_authorized_user()) [OM] - die("unauthorized"); [OM] - sensitive_stuff(spanning, [OM] - multiple, [OM] - lines); [OM] -} void another_function() { [del] - printf("foo"); [add] + printf("bar"); } [NM] +void sensitive_stuff(void) [NM] +{ [NM] + if (!is_authorized_user()) [NM] + die("unauthorized"); [NM] + sensitive_stuff(spanning, [NM] + multiple, [NM] + lines); [NM] +} However adjacent blocks may be problematic. For example, in this potentially malicious patch, the swapping of blocks can be spotted: [OM] -void sensitive_stuff(void) [OM] -{ [OMA] - if (!is_authorized_user()) [OMA] - die("unauthorized"); [OM] - sensitive_stuff(spanning, [OM] - multiple, [OM] - lines); [OMA] -} void another_function() { [del] - printf("foo"); [add] + printf("bar"); } [NM] +void sensitive_stuff(void) [NM] +{ [NMA] + sensitive_stuff(spanning, [NMA] + multiple, [NMA] + lines); [NM] + if (!is_authorized_user()) [NM] + die("unauthorized"); [NMA] +} If the moved code is larger, it is easier to hide some permutation in the code, which is why some alternative coloring is needed. This patch implements the first mode: * basic alternating 'Zebra' mode This conveys all information needed to the user. Defer customization to later patches. First I implemented an alternative design, which would try to fingerprint a line by its neighbors to detect if we are in a block or at the boundary. This idea iss error prone as it inspected each line and its neighboring lines to determine if the line was (a) moved and (b) if was deep inside a hunk by having matching neighboring lines. This is unreliable as the we can construct hunks which have equal neighbors that just exceed the number of lines inspected. (Think of 'AXYZBXYZCXYZD..' with each letter as a line, that is permutated to AXYZCXYZBXYZD..'). Instead this provides a dynamic programming greedy algorithm that finds the largest moved hunk and then has several modes on highlighting bounds. A note on the options '--submodule=diff' and '--color-words/--word-diff': In the conversion to use emit_line in the prior patches both submodules as well as word diff output carefully chose to call emit_line with sign=0. All output with sign=0 is ignored for move detection purposes in this patch, such that no weird looking output will be generated for these cases. This leads to another thought: We could pass on '--color-moved' to submodules such that they color up moved lines for themselves. If we'd do so only line moves within a repository boundary are marked up. It is useful to have moved lines colored, but there are annoying corner cases, such as a single line moved, that is very common. For example in a typical patch of C code, we have closing braces that end statement blocks or functions. While it is technically true that these lines are moved as they show up elsewhere, it is harmful for the review as the reviewers attention is drawn to such a minor side annoyance. For now let's have a simple solution of hardcoding the number of moved lines to be at least 3 before coloring them. Note, that the length is applied across all blocks to find the 'lonely' blocks that pollute new code, but do not interfere with a permutated block where each permutation has less lines than 3. Helped-by: Jonathan Tan Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

diff.c: buffer all output if asked to

2017-06-30T20:13:02Z

Introduce a new option 'emitted_symbols' in the struct diff_options which controls whether all output is buffered up until all output is available. It is set internally in diff.c when necessary. We'll have a new struct 'emitted_string' in diff.c which will be used to buffer each line. The emitted_string will duplicate the memory of the line to buffer as that is easiest to reason about for now. In a future patch we may want to decrease the memory usage by not duplicating all output for buffering but rather we may want to store offsets into the file or in case of hunk descriptions such as the similarity score, we could just store the relevant number and reproduce the text later on. This approach was chosen as a first step because it is quite simple compared to the alternative with less memory footprint. emit_diff_symbol factors out the emission part and depending on the diff_options->emitted_symbols the emission will be performed directly when calling emit_diff_symbol or after the whole process is done, i.e. by buffering we have add the possibility for a second pass over the whole output before doing the actual output. In 6440d34 (2012-03-14, diff: tweak a _copy_ of diff_options with word-diff) we introduced a duplicate diff options struct for word emissions as we may have different regex settings in there. When buffering the output, we need to operate on just one buffer, so we have to copy back the emissions of the word buffer into the main buffer. Unconditionally enable output via buffer in this patch as it yields a great opportunity for testing, i.e. all the diff tests from the test suite pass without having reordering issues (i.e. only parts of the output got buffered, and we forgot to buffer other parts). The test suite passes, which gives confidence that we converted all functions to use emit_string for output. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

diff.c: convert show_stats to use emit_diff_symbol

2017-06-30T20:13:02Z

We call print_stat_summary from builtin/apply, so we still need the version with a file pointer, so introduce print_stat_summary_0 that uses emit_string machinery and keep print_stat_summary with the same arguments around. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

submodule.c: migrate diff output to use emit_diff_symbol

2017-06-30T20:13:02Z

As the submodule process is no longer attached to the same file pointer 'o->file' as the superprojects process, there is a different result in color.c::check_auto_color. That is why we need to pass coloring explicitly, such that the submodule coloring decision will be made by the child process processing the submodule. Only DIFF_SYMBOL_SUBMODULE_PIPETHROUGH contains color, the other symbols are for embedding the submodule output into the superprojects output. Remove the colors from the function signatures, as all the coloring decisions will be made either inside the child process or the final emit_diff_symbol, but not in the functions driving the submodule diff. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

diff.c: migrate emit_line_checked to use emit_diff_symbol

2017-06-30T20:13:01Z

Add a new flags field to emit_diff_symbol, that will be used by context lines for: * white space rules that are applicable (The first 12 bits) Take a note in cahe.c as well, when this ws rules are extended we have to fix the bits in the flags field. * how the rules are evaluated (actually this double encodes the sign of the line, but the code is easier to keep this way, bits 13,14,15) * if the line a blank line at EOF (bit 16) The check if new lines need to be marked up as extra lines at the end of file, is now done unconditionally. That should be ok, as 'new_blank_line_at_eof' has a quick early return. Signed-off-by: Stefan Beller Signed-off-by: Junio C Hamano

Merge branch 'bw/object-id'

2017-06-19T19:38:44Z

Conversion from uchar[20] to struct object_id continues. * bw/object-id: (33 commits) diff: rename diff_fill_sha1_info to diff_fill_oid_info diffcore-rename: use is_empty_blob_oid tree-diff: convert path_appendnew to object_id tree-diff: convert diff_tree_paths to struct object_id tree-diff: convert try_to_follow_renames to struct object_id builtin/diff-tree: cleanup references to sha1 diff-tree: convert diff_tree_sha1 to struct object_id notes-merge: convert write_note_to_worktree to struct object_id notes-merge: convert verify_notes_filepair to struct object_id notes-merge: convert find_notes_merge_pair_ps to struct object_id notes-merge: convert merge_from_diffs to struct object_id notes-merge: convert notes_merge* to struct object_id tree-diff: convert diff_root_tree_sha1 to struct object_id combine-diff: convert find_paths_* to struct object_id combine-diff: convert diff_tree_combined to struct object_id diff: convert diff_flush_patch_id to struct object_id patch-ids: convert to struct object_id diff: finish conversion for prepare_temp_file to struct object_id diff: convert reuse_worktree_file to struct object_id diff: convert fill_filespec to struct object_id ...

tree-diff: convert diff_tree_paths to struct object_id

2017-06-05T02:23:58Z

Signed-off-by: Brandon Williams Signed-off-by: Junio C Hamano