git diff -h help is succinct, but perhaps too much so. The symmetric-diff syntax, git diff A...B, is defined by the documentation to compare the merge base of A and B to commit B. It does so just fine when there is a merge base. It compares A and B directly if there is no merge base, and it is overly forgiving of bad arguments after which it can produce nonsensical diffs. It also behaves badly with other odd/incorrect usages, such as git diff A..B C..D. The first patch simply adjusts a test that will fail if the second patch is accepted. The second patch adds special handling for the symmetric diff syntax so that the option parsing works, plus a small test suite. The third patch updates the documentation, including adding a section for combined commits, and makes the help output more verbose (to match the SYNOPSIS and provide common diff options like git-diff-files, for instance). Changes since v1: * updated commit messages * rewrote prepare function * added tests to reject bad two-dot usage as well * removed A..B syntax from usage (and fixed typo) * fixed up three-dot synopsis text Chris Torek (3): t/t3430: avoid undefined git diff behavior git diff: improve range handling Documentation: usage for diff combined commits Documentation/git-diff.txt | 20 ++++-- builtin/diff.c | 132 +++++++++++++++++++++++++++++++++---- t/t3430-rebase-merges.sh | 2 +- t/t4068-diff-symmetric.sh | 91 +++++++++++++++++++++++++ 4 files changed, 226 insertions(+), 19 deletions(-) create mode 100755 t/t4068-diff-symmetric.sh base-commit: 20514004ddf1a3528de8933bc32f284e175e1012 Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-804%2Fchris3torek%2Fcleanup-diff-v3 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-804/chris3torek/cleanup-diff-v3 Pull-Request: https://github.com/git/git/pull/804 Range-diff vs v2: 1: 2ccaad645ff = 1: 2ccaad645ff t/t3430: avoid undefined git diff behavior 2: 100fa403477 ! 2: 60aed3f9d65 git diff: improve A...B merge-base handling @@ Metadata Author: Chris Torek <chris.torek@xxxxxxxxx> ## Commit message ## - git diff: improve A...B merge-base handling + git diff: improve range handling When git diff is given a symmetric difference A...B, it chooses some merge base from the two specified commits (as documented). @@ Commit message lost. We will produce a combined diff instead. Similar weirdness occurs if you use, e.g., "git diff C A...B D". + Likewise, using multiple two-dot ranges, or tossing extra + revision specifiers into the command line with two-dot ranges, + or mixing two and three dot ranges, all produce nonsense. - To avoid all this, add a routine to catch the A...B case and verify that - there is at least one merge base, and that the arguments make sense. - As a side effect, produce a warning showing *which* merge base is being - used when there are multiple choices; die if there is no merge base. + To avoid all this, add a routine to catch the range cases and + verify that that the arguments make sense. As a side effect, + produce a warning showing *which* merge base is being used when + there are multiple choices; die if there is no merge base. Signed-off-by: Chris Torek <chris.torek@xxxxxxxxx> @@ builtin/diff.c: static int builtin_diff_files(struct rev_info *revs, int argc, c } +struct symdiff { -+ struct bitmap *skip; /* bitmap of commit indices to skip, or NULL */ -+ int warn; /* true if there were multiple merge bases */ -+ int base, left, right; /* index of chosen merge base and left&right */ ++ struct bitmap *skip; ++ int warn; ++ const char *base, *left, *right; +}; + +/* + * Check for symmetric-difference arguments, and if present, arrange -+ * everything we need to know to handle them correctly. ++ * everything we need to know to handle them correctly. As a bonus, ++ * weed out all bogus range-based revision specifications, e.g., ++ * "git diff A..B C..D" or "git diff A..B C" get rejected. + * + * For an actual symmetric diff, *symdiff is set this way: + * @@ builtin/diff.c: static int builtin_diff_files(struct rev_info *revs, int argc, c + * which there might be many, and A in A...B). Note that the + * chosen merge base and right side are NOT marked. + * - warn is set if there are multiple merge bases. -+ * - base, left, and right hold the merge base and left and -+ * right side indices, for warnings or errors. ++ * - base, left, and right point to the names to use in a ++ * warning about multiple merge bases. + * + * If there is no symmetric diff argument, sym->skip is NULL and + * sym->warn is cleared. The remaining fields are not set. -+ * -+ * If the user provides a symmetric diff with no merge base, or -+ * more than one range, we do a usage-exit. + */ +static void symdiff_prepare(struct rev_info *rev, struct symdiff *sym) +{ -+ int i, lcount = 0, rcount = 0, basecount = 0; ++ int i, is_symdiff = 0, basecount = 0, othercount = 0; + int lpos = -1, rpos = -1, basepos = -1; + struct bitmap *map = NULL; + @@ builtin/diff.c: static int builtin_diff_files(struct rev_info *revs, int argc, c + basecount++; + break; /* do mark all bases */ + case REV_CMD_LEFT: ++ if (lpos > 0) ++ usage(builtin_diff_usage); ++ lpos = i; + if (obj->flags & SYMMETRIC_LEFT) { -+ lpos = i; -+ lcount++; ++ is_symdiff = 1; + break; /* do mark A */ + } + continue; + case REV_CMD_RIGHT: ++ if (rpos > 0) ++ usage(builtin_diff_usage); + rpos = i; -+ rcount++; + continue; /* don't mark B */ -+ default: ++ case REV_CMD_PARENTS_ONLY: ++ case REV_CMD_REF: ++ case REV_CMD_REV: ++ othercount++; + continue; + } + if (map == NULL) @@ builtin/diff.c: static int builtin_diff_files(struct rev_info *revs, int argc, c + bitmap_set(map, i); + } + -+ if (lcount == 0) { /* not a symmetric difference */ ++ /* ++ * Forbid any additional revs for both A...B and A..B. ++ */ ++ if (lpos >= 0 && othercount > 0) ++ usage(builtin_diff_usage); ++ ++ if (!is_symdiff) { + bitmap_free(map); + sym->warn = 0; + sym->skip = NULL; + return; + } + -+ if (lcount != 1) -+ die(_("cannot use more than one symmetric difference")); -+ -+ if (basecount == 0) { -+ const char *lname = rev->pending.objects[lpos].name; -+ const char *rname = rev->pending.objects[rpos].name; -+ die(_("%s...%s: no merge base"), lname, rname); -+ } ++ sym->left = rev->pending.objects[lpos].name; ++ sym->right = rev->pending.objects[rpos].name; ++ sym->base = rev->pending.objects[basepos].name; ++ if (basecount == 0) ++ die(_("%s...%s: no merge base"), sym->left, sym->right); + bitmap_unset(map, basepos); /* unmark the base we want */ -+ sym->base = basepos; -+ sym->left = lpos; -+ sym->right = rpos; + sym->warn = basecount > 1; + sym->skip = map; +} @@ builtin/diff.c: int cmd_diff(int argc, const char **argv, const char *prefix) struct object_array_entry *entry = &rev.pending.objects[i]; struct object *obj = entry->item; @@ builtin/diff.c: int cmd_diff(int argc, const char **argv, const char *prefix) - die(_("invalid object '%s' given."), name); - if (obj->type == OBJ_COMMIT) obj = &get_commit_tree(((struct commit *)obj))->object; -- + if (obj->type == OBJ_TREE) { + if (sdiff.skip && bitmap_get(sdiff.skip, i)) + continue; @@ builtin/diff.c: int cmd_diff(int argc, const char **argv, const char *prefix) result = builtin_diff_index(&rev, argc, argv); - else if (ent.nr == 2) + else if (ent.nr == 2) { -+ if (sdiff.warn) { -+ const char *lname = rev.pending.objects[sdiff.left].name; -+ const char *rname = rev.pending.objects[sdiff.right].name; -+ const char *basename = rev.pending.objects[sdiff.base].name; ++ if (sdiff.warn) + warning(_("%s...%s: multiple merge bases, using %s"), -+ lname, rname, basename); -+ } ++ sdiff.left, sdiff.right, sdiff.base); result = builtin_diff_tree(&rev, argc, argv, &ent.objects[0], &ent.objects[1]); - else if (ent.objects[0].item->flags & UNINTERESTING) { @@ builtin/diff.c: int cmd_diff(int argc, const char **argv, const char *prefix) - result = builtin_diff_tree(&rev, argc, argv, - &ent.objects[0], - &ent.objects[ent.nr-1]); -- } else -+ } else { -+ if (sdiff.skip) -+ usage(builtin_diff_usage); + } else result = builtin_diff_combined(&rev, argc, argv, ent.objects, ent.nr); -+ } - result = diff_result_code(&rev.diffopt, result); - if (1 < rev.diffopt.skip_stat_unmatch) - refresh_index_quietly(); ## t/t4068-diff-symmetric.sh (new) ## @@ @@ t/t4068-diff-symmetric.sh (new) + +test_expect_success 'diff with one merge base' ' + git diff commit-D...br1 >tmp && -+ tail -1 tmp >actual && ++ tail -n 1 tmp >actual && + echo +f >expect && + test_cmp expect actual +' @@ t/t4068-diff-symmetric.sh (new) + +test_expect_success 'diff with too many symmetric differences' ' + test_must_fail git diff br1...master br2...br3 >tmp 2>err && -+ test_i18ngrep "fatal: cannot use more than one symmetric difference" err ++ test_i18ngrep "usage" err +' + +test_expect_success 'diff with symmetric difference and extraneous arg' ' @@ t/t4068-diff-symmetric.sh (new) + test_i18ngrep "usage" err +' + ++test_expect_success 'diff with two ranges' ' ++ test_must_fail git diff master br1..master br2..br3 >tmp 2>err && ++ test_i18ngrep "usage" err ++' ++ ++test_expect_success 'diff with ranges and extra arg' ' ++ test_must_fail git diff master br1..master commit-D >tmp 2>err && ++ test_i18ngrep "usage" err ++' ++ +test_done 3: b9b4c6f113d ! 3: a7da92cd635 Documentation: tweak git diff help slightly @@ Metadata Author: Chris Torek <chris.torek@xxxxxxxxx> ## Commit message ## - Documentation: tweak git diff help slightly + Documentation: usage for diff combined commits - Update the manual page synopsis to include the three-dot notation - and the combined-diff option + Document the usage for producing combined commits with "git diff". + This includes updating the synopsis section. + + While here, add the three-dot notation to the synopsis. Make "git diff -h" print the same usage summary as the manual page synopsis, minus the "A..B" form, which is now discouraged. - Document the usage for producing combined commits. - Signed-off-by: Chris Torek <chris.torek@xxxxxxxxx> ## Documentation/git-diff.txt ## @@ Documentation/git-diff.txt: two blob objects, or changes between two files on di + This form is to view the results of a merge commit. The first + listed <commit> must be the merge itself; the remaining two or + more commits should be its parents. A convenient way to produce -+ the desired set of revisions is to use the {caret}@ suffix, i.e., -+ "git diff master master^@". This is equivalent to running "git -+ show --format=" on the merge commit, e.g., "git show --format= -+ master". ++ the desired set of revisions is to use the {caret}@ suffix. ++ For instance, if `master` names a merge commit, `git diff master ++ master^@` gives the same combined diff as `git show master`. + 'git diff' [<options>] <commit>\...<commit> [--] [<path>...]:: -- gitgitgadget
