The range-notation in `git diff` has been cited as a mistake since diff compares two endpoints, not whole ranges.[0] In fact, the ranges seem to take on the opposite meanings when compared to range notation in `git log`. In an effort to reduce the use of range notation as much as possible, introduce the `--merge-base` flag, slightly modified from a suggestion by Jonathan Nieder.[1] This flag allows us to replace the first commit given on the command-line with its merge base between the first and second commits. One additional bonus is that this flag allows the "after" side to be not just constrained to a commit (like with `...` notation). It can now be the working tree or the index as well. The `--merge-base` name isn't very satisfying. If anyone has any better suggestions, please let me know. Changes since v1: * Implement Junio's documentation suggestions * Update git diff's usage to include this option Changes since v2: * Teach diff-index and diff-tree the --merge-base option as well Changes since v3: * Don't use bitfields directly; extract them to an intermediate variable * Use explicit literals in diff_get_merge_base() for clarity * Fix xstrdup() leak * I misunderstood and thought we wanted to deprecate `...` notation; this is not the case so remove all references to "gentle deprecation" and don't remove usage text that references it [0]: https://lore.kernel.org/git/xmqqy2v26hu0.fsf@xxxxxxxxxxxxxxxxxxxxxxxxx/ [1]: https://lore.kernel.org/git/20191223215928.GB38316@xxxxxxxxxx/ Denton Liu (10): t4068: remove unnecessary >tmp git-diff-index.txt: make --cached description a proper sentence git-diff.txt: backtick quote command text contrib/completion: extract common diff/difftool options diff-lib: accept option flags in run_diff_index() diff-lib: define diff_get_merge_base() t4068: add --merge-base tests builtin/diff-index: learn --merge-base builtin/diff-tree: learn --merge-base contrib/completion: complete `git diff --merge-base` Documentation/git-diff-index.txt | 9 +- Documentation/git-diff-tree.txt | 7 +- Documentation/git-diff.txt | 36 +++-- builtin/diff-index.c | 10 +- builtin/diff-tree.c | 18 +++ builtin/diff.c | 49 +++++-- contrib/completion/git-completion.bash | 15 +- diff-lib.c | 63 +++++++- diff.h | 7 +- t/t4068-diff-symmetric-merge-base.sh | 193 +++++++++++++++++++++++++ t/t4068-diff-symmetric.sh | 91 ------------ 11 files changed, 358 insertions(+), 140 deletions(-) create mode 100755 t/t4068-diff-symmetric-merge-base.sh delete mode 100755 t/t4068-diff-symmetric.sh Range-diff against v3: 1: 80e9066a59 = 1: 80e9066a59 t4068: remove unnecessary >tmp 2: 21b20281e6 = 2: 21b20281e6 git-diff-index.txt: make --cached description a proper sentence 3: ca9568c2ea = 3: ca9568c2ea git-diff.txt: backtick quote command text 4: 1ac8459541 = 4: 1ac8459541 contrib/completion: extract common diff/difftool options 5: 496908ac10 ! 5: 99d8b51585 diff-lib: accept option flags in run_diff_index() @@ diff-lib.c: static int diff_cache(struct rev_info *revs, +int run_diff_index(struct rev_info *revs, unsigned int option) { struct object_array_entry *ent; ++ int cached = !!(option & DIFF_INDEX_CACHED); -@@ diff-lib.c: int run_diff_index(struct rev_info *revs, int cached) - - trace_performance_enter(); - ent = revs->pending.objects; -- if (diff_cache(revs, &ent->item->oid, ent->name, cached)) -+ if (diff_cache(revs, &ent->item->oid, ent->name, !!(option & DIFF_INDEX_CACHED))) - exit(128); - -- diff_set_mnemonic_prefix(&revs->diffopt, "c/", cached ? "i/" : "w/"); -+ diff_set_mnemonic_prefix(&revs->diffopt, "c/", (option & DIFF_INDEX_CACHED) ? "i/" : "w/"); - diffcore_fix_diff_index(); - diffcore_std(&revs->diffopt); - diff_flush(&revs->diffopt); + if (revs->pending.nr != 1) + BUG("run_diff_index must be passed exactly one tree"); ## diff.h ## @@ diff.h: const char *diff_aligned_abbrev(const struct object_id *sha1, int); @@ diff.h: const char *diff_aligned_abbrev(const struct object_id *sha1, int); #define DIFF_RACY_IS_MODIFIED 02 int run_diff_files(struct rev_info *revs, unsigned int option); -int run_diff_index(struct rev_info *revs, int cached); ++ +#define DIFF_INDEX_CACHED 01 +int run_diff_index(struct rev_info *revs, unsigned int option); 6: 6aac57ca02 ! 6: 3287e649f1 diff-lib: define diff_get_merge_base() @@ diff-lib.c: static int diff_cache(struct rev_info *revs, + * ranges produce three pending commits, resulting in a + * misleading error message. + */ -+ if (revs->pending.nr > ARRAY_SIZE(mb_child)) -+ die(_("--merge-base does not work with more than two commits")); ++ if (revs->pending.nr < 1 || revs->pending.nr > 2) ++ BUG("unexpected revs->pending.nr: %d", revs->pending.nr); + + for (i = 0; i < revs->pending.nr; i++) + mb_child[i] = lookup_commit_reference(the_repository, &revs->pending.objects[i].item->oid); -+ if (revs->pending.nr < ARRAY_SIZE(mb_child)) { ++ if (revs->pending.nr == 1) { + struct object_id oid; + -+ if (revs->pending.nr != 1) -+ BUG("unexpected revs->pending.nr: %d", revs->pending.nr); -+ + if (get_oid("HEAD", &oid)) + die(_("unable to get HEAD")); + 7: c9225a0440 = 7: 27930d4476 t4068: add --merge-base tests 8: 1e4f805e57 ! 8: f54baa4ecd builtin/diff-index: learn --merge-base @@ builtin/diff.c: static int builtin_diff_index(struct rev_info *revs, argv++; argc--; ## diff-lib.c ## -@@ diff-lib.c: void diff_get_merge_base(const struct rev_info *revs, struct object_id *mb) - int run_diff_index(struct rev_info *revs, unsigned int option) +@@ diff-lib.c: int run_diff_index(struct rev_info *revs, unsigned int option) { struct object_array_entry *ent; + int cached = !!(option & DIFF_INDEX_CACHED); ++ int merge_base = !!(option & DIFF_INDEX_MERGE_BASE); + struct object_id oid; + const char *name; ++ char merge_base_hex[GIT_MAX_HEXSZ + 1]; if (revs->pending.nr != 1) BUG("run_diff_index must be passed exactly one tree"); trace_performance_enter(); ent = revs->pending.objects; -- if (diff_cache(revs, &ent->item->oid, ent->name, !!(option & DIFF_INDEX_CACHED))) +- if (diff_cache(revs, &ent->item->oid, ent->name, cached)) + -+ if (option & DIFF_INDEX_MERGE_BASE) { ++ if (merge_base) { + diff_get_merge_base(revs, &oid); -+ name = xstrdup(oid_to_hex(&oid)); ++ name = oid_to_hex_r(merge_base_hex, &oid); + } else { + oidcpy(&oid, &ent->item->oid); + name = ent->name; + } + -+ if (diff_cache(revs, &oid, name, !!(option & DIFF_INDEX_CACHED))) ++ if (diff_cache(revs, &oid, name, cached)) exit(128); - diff_set_mnemonic_prefix(&revs->diffopt, "c/", (option & DIFF_INDEX_CACHED) ? "i/" : "w/"); + diff_set_mnemonic_prefix(&revs->diffopt, "c/", cached ? "i/" : "w/"); ## diff.h ## @@ diff.h: void diff_get_merge_base(const struct rev_info *revs, struct object_id *mb); - #define DIFF_RACY_IS_MODIFIED 02 int run_diff_files(struct rev_info *revs, unsigned int option); + #define DIFF_INDEX_CACHED 01 +#define DIFF_INDEX_MERGE_BASE 02 int run_diff_index(struct rev_info *revs, unsigned int option); 9: c0d27b125e ! 9: 4880d21119 builtin/diff-tree: learn --merge-base @@ Metadata ## Commit message ## builtin/diff-tree: learn --merge-base - In order to get the diff between a commit and its merge base, the - currently preferred method is to use `git diff A...B`. However, the - range-notation with diff has, time and time again, been noted as a point - of confusion and thus, it should be avoided. Although we have a - substitute for the double-dot notation, we don't have any replacement - for the triple-dot notation. + The previous commit introduced ---merge-base a way to take the diff + between the working tree or index and the merge base between an arbitrary + commit and HEAD. It makes sense to extend this option to support the + case where two commits are given too and behave in a manner identical to + `git diff A...B`. - Introduce the --merge-base flag as a replacement for triple-dot + Introduce the --merge-base flag as an alternative to triple-dot notation. Thus, we would be able to write the above as - `git diff --merge-base A B`, allowing us to gently deprecate - range-notation completely. + `git diff --merge-base A B`. ## Documentation/git-diff-tree.txt ## @@ Documentation/git-diff-tree.txt: SYNOPSIS @@ Documentation/git-diff.txt: SYNOPSIS 'git diff' [<options>] [<commit>] [--] [<path>...] 'git diff' [<options>] --cached [--merge-base] [<commit>] [--] [<path>...] -'git diff' [<options>] <commit> [<commit>...] <commit> [--] [<path>...] --'git diff' [<options>] <commit>...<commit> [--] [<path>...] +'git diff' [<options>] [--merge-base] <commit> [<commit>...] <commit> [--] [<path>...] + 'git diff' [<options>] <commit>...<commit> [--] [<path>...] 'git diff' [<options>] <blob> <blob> 'git diff' [<options>] --no-index [--] <path> <path> - @@ Documentation/git-diff.txt: of <commit> and HEAD. `git diff --merge-base A` is equivalent to branch name to compare with the tip of a different branch. @@ builtin/diff.c "git diff [<options>] [<commit>] [--] [<path>...]\n" " or: git diff [<options>] --cached [<commit>] [--] [<path>...]\n" -" or: git diff [<options>] <commit> [<commit>...] <commit> [--] [<path>...]\n" --" or: git diff [<options>] <commit>...<commit>] [--] [<path>...]\n" +" or: git diff [<options>] <commit> [--merge-base] [<commit>...] <commit> [--] [<path>...]\n" + " or: git diff [<options>] <commit>...<commit>] [--] [<path>...]\n" " or: git diff [<options>] <blob> <blob>]\n" " or: git diff [<options>] --no-index [--] <path> <path>]\n" - COMMON_DIFF_OPTIONS_HELP; @@ builtin/diff.c: static int builtin_diff_tree(struct rev_info *revs, struct object_array_entry *ent1) { 10: 42a8c9b665 = 10: 32e3e52b5f contrib/completion: complete `git diff --merge-base` -- 2.28.0.760.g8d73e04208
