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.
Introduce the --merge-base flag as a replacement for 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.
Signed-off-by: Denton Liu <liu.denton@xxxxxxxxx>
---
Documentation/git-diff-tree.txt | 7 ++++-
Documentation/git-diff.txt | 9 ++++---
builtin/diff-tree.c | 18 +++++++++++++
builtin/diff.c | 40 +++++++++++++++++++---------
t/t4068-diff-symmetric-merge-base.sh | 34 +++++++++++++++++++++++
5 files changed, 91 insertions(+), 17 deletions(-)
diff --git a/Documentation/git-diff-tree.txt b/Documentation/git-diff-tree.txt
index 5c8a2a5e97..2fc24c542f 100644
--- a/Documentation/git-diff-tree.txt
+++ b/Documentation/git-diff-tree.txt
@@ -10,7 +10,7 @@ SYNOPSIS
--------
[verse]
'git diff-tree' [--stdin] [-m] [-s] [-v] [--no-commit-id] [--pretty]
- [-t] [-r] [-c | --cc] [--combined-all-paths] [--root]
+ [-t] [-r] [-c | --cc] [--combined-all-paths] [--root] [--merge-base]
[<common diff options>] <tree-ish> [<tree-ish>] [<path>...]
DESCRIPTION
@@ -43,6 +43,11 @@ include::diff-options.txt[]
When `--root` is specified the initial commit will be shown as a big
creation event. This is equivalent to a diff against the NULL tree.
+--merge-base::
+ Instead of comparing the <tree-ish>s directly, use the merge
+ base between the two <tree-ish>s as the "before" side. There
+ must be two <tree-ish>s given and they must both be commits.
+
--stdin::
When `--stdin` is specified, the command does not take
<tree-ish> arguments from the command line. Instead, it
diff --git a/Documentation/git-diff.txt b/Documentation/git-diff.txt
index 762ee6d074..d3b526e00a 100644
--- a/Documentation/git-diff.txt
+++ b/Documentation/git-diff.txt
@@ -11,8 +11,7 @@ SYNOPSIS
[verse]
'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>] <blob> <blob>
'git diff' [<options>] --no-index [--] <path> <path>
@@ -62,10 +61,14 @@ of <commit> and HEAD. `git diff --merge-base A` is equivalent to
branch name to compare with the tip of a different
branch.
-'git diff' [<options>] <commit> <commit> [--] [<path>...]::
+'git diff' [<options>] [--merge-base] <commit> <commit> [--] [<path>...]::
This is to view the changes between two arbitrary
<commit>.
++
+If --merge-base is given, use the merge base of the two commits for the
+"before" side. `git diff --merge-base A B` is equivalent to
+`git diff $(git merge-base A B) B`.
'git diff' [<options>] <commit> <commit>... <commit> [--] [<path>...]::
diff --git a/builtin/diff-tree.c b/builtin/diff-tree.c
index 802363d0a2..823d6678e5 100644
--- a/builtin/diff-tree.c
+++ b/builtin/diff-tree.c
@@ -111,6 +111,7 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
struct setup_revision_opt s_r_opt;
struct userformat_want w;
int read_stdin = 0;
+ int merge_base = 0;
if (argc == 2 && !strcmp(argv[1], "-h"))
usage(diff_tree_usage);
@@ -143,9 +144,26 @@ int cmd_diff_tree(int argc, const char **argv, const char *prefix)
read_stdin = 1;
continue;
}
+ if (!strcmp(arg, "--merge-base")) {
+ merge_base = 1;
+ continue;
+ }
usage(diff_tree_usage);
}
+ if (read_stdin && merge_base)
+ die(_("--stdin and --merge-base are mutually exclusive"));
+
+ if (merge_base) {
+ struct object_id oid;
+
+ if (opt->pending.nr != 2)
+ die(_("--merge-base only works with two commits"));
+
+ diff_get_merge_base(opt, &oid);
+ opt->pending.objects[0].item = lookup_object(the_repository, &oid);
+ }
+
/*
* NOTE! We expect "a..b" to expand to "^a b" but it is
* perfectly valid for revision range parser to yield "b ^a",
diff --git a/builtin/diff.c b/builtin/diff.c
index 1baea18ae0..ad78bc89b3 100644
--- a/builtin/diff.c
+++ b/builtin/diff.c
@@ -26,8 +26,7 @@
static const char builtin_diff_usage[] =
"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>] <blob> <blob>]\n"
" or: git diff [<options>] --no-index [--] <path> <path>]\n"
COMMON_DIFF_OPTIONS_HELP;
@@ -172,19 +171,34 @@ static int builtin_diff_tree(struct rev_info *revs,
struct object_array_entry *ent1)
{
const struct object_id *(oid[2]);
- int swap = 0;
+ struct object_id mb_oid;
+ int merge_base = 0;
- if (argc > 1)
- usage(builtin_diff_usage);
+ while (1 < argc) {
+ const char *arg = argv[1];
+ if (!strcmp(arg, "--merge-base"))
+ merge_base = 1;
+ else
+ usage(builtin_diff_usage);
+ argv++; argc--;
+ }
- /*
- * We saw two trees, ent0 and ent1. If ent1 is uninteresting,
- * swap them.
- */
- if (ent1->item->flags & UNINTERESTING)
- swap = 1;
- oid[swap] = &ent0->item->oid;
- oid[1 - swap] = &ent1->item->oid;
+ if (merge_base) {
+ diff_get_merge_base(revs, &mb_oid);
+ oid[0] = &mb_oid;
+ oid[1] = &revs->pending.objects[1].item->oid;
+ } else {
+ int swap = 0;
+
+ /*
+ * We saw two trees, ent0 and ent1. If ent1 is uninteresting,
+ * swap them.
+ */
+ if (ent1->item->flags & UNINTERESTING)
+ swap = 1;
+ oid[swap] = &ent0->item->oid;
+ oid[1 - swap] = &ent1->item->oid;
+ }
diff_tree_oid(oid[0], oid[1], "", &revs->diffopt);
log_tree_diff_flush(revs);
return 0;
diff --git a/t/t4068-diff-symmetric-merge-base.sh b/t/t4068-diff-symmetric-merge-base.sh
index 49432379cb..03487cc945 100755
--- a/t/t4068-diff-symmetric-merge-base.sh
+++ b/t/t4068-diff-symmetric-merge-base.sh
@@ -156,4 +156,38 @@ do
'
done
+for cmd in diff-tree diff
+do
+ test_expect_success "$cmd --merge-base with two commits" '
+ git $cmd commit-C master >expect &&
+ git $cmd --merge-base br2 master >actual &&
+ test_cmp expect actual
+ '
+
+ test_expect_success "$cmd --merge-base commit and non-commit" '
+ test_must_fail git $cmd --merge-base br2 master^{tree} 2>err &&
+ test_i18ngrep "fatal: --merge-base only works with commits" err
+ '
+
+ test_expect_success "$cmd --merge-base with no merge bases and two commits" '
+ test_must_fail git $cmd --merge-base br2 br3 2>err &&
+ test_i18ngrep "fatal: no merge base found" err
+ '
+
+ test_expect_success "$cmd --merge-base with multiple merge bases and two commits" '
+ test_must_fail git $cmd --merge-base master br1 2>err &&
+ test_i18ngrep "fatal: multiple merge bases found" err
+ '
+done
+
+test_expect_success 'diff-tree --merge-base with one commit' '
+ test_must_fail git diff-tree --merge-base master 2>err &&
+ test_i18ngrep "fatal: --merge-base only works with two commits" err
+'
+
+test_expect_success 'diff --merge-base with range' '
+ test_must_fail git diff --merge-base br2..br3 2>err &&
+ test_i18ngrep "fatal: --merge-base does not work with ranges" err
+'
+
test_done
--
2.28.0.618.gf4bc123cb7
