revision: add --maximal-only option
When inspecting a range of commits from some set of starting references, it is sometimes useful to learn which commits are not reachable from any other commits in the selected range. One such application is in the creation of a sequence of bundles for the bundle URI feature. Creating a stack of bundles representing different slices of time includes defining which references to include. If all references are used, then this may be overwhelming or redundant. Instead, selecting commits that are maximal to the range could help defining a smaller reference set to use in the bundle header. Add a new '--maximal-only' option to restrict the output of a revision range to be only the commits that are not reachable from any other commit in the range, based on the reachability definition of the walk. This is accomplished by adding a new 28th bit flag, CHILD_VISITED, that is set as we walk. This does extend the bit range in object.h, but using an earlier bit may collide with another feature. The tests demonstrate the behavior of the feature with a positive-only range, ranges with negative references, and walk-modifying flags like --first-parent and --exclude-first-parent-only. Since the --boundary option would not increase any results when used with the --maximal-only option, mark them as incompatible. Signed-off-by: Derrick Stolee <stolee@gmail.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Derrick Stolee committed
Jan 22, 2026 at 16:05 UTC
b4e8f60a3c78477e1f28b052cd740ac4a43741d5
6 files changed
+110
-5
Documentation/rev-list-options.adoc
+4
@@ -148,6 +148,10 @@ endif::git-log[]
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from the point where it diverged from the remote branch, given
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that arbitrary merges can be valid topic branch changes.
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+`--maximal-only`::
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+ Restrict the output commits to be those that are not reachable
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+ from any other commits in the revision range.
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+
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`--not`::
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Reverses the meaning of the '{caret}' prefix (or lack thereof)
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for all following revision specifiers, up to the next `--not`.
object.h
+2
-2
@@ -64,7 +64,7 @@ void object_array_init(struct object_array *array);
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/*
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* object flag allocation:
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- * revision.h: 0---------10 15 23------27
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+ * revision.h: 0---------10 15 23--------28
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* fetch-pack.c: 01 67
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* negotiator/default.c: 2--5
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* walker.c: 0-2
@@ -86,7 +86,7 @@ void object_array_init(struct object_array *array);
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* builtin/unpack-objects.c: 2021
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* pack-bitmap.h: 2122
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*/
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-#define FLAG_BITS 28
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+#define FLAG_BITS 29
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#define TYPE_BITS 3
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revision.c
+10
-2
@@ -1150,7 +1150,8 @@ static int process_parents(struct rev_info *revs, struct commit *commit,
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struct commit *p = parent->item;
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parent = parent->next;
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if (p)
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- p->object.flags |= UNINTERESTING;
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+ p->object.flags |= UNINTERESTING |
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+ CHILD_VISITED;
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if (repo_parse_commit_gently(revs->repo, p, 1) < 0)
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continue;
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if (p->parents)
@@ -1204,7 +1205,7 @@ static int process_parents(struct rev_info *revs, struct commit *commit,
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if (!*slot)
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*slot = *revision_sources_at(revs->sources, commit);
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}
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- p->object.flags |= pass_flags;
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+ p->object.flags |= pass_flags | CHILD_VISITED;
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if (!(p->object.flags & SEEN)) {
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p->object.flags |= (SEEN | NOT_USER_GIVEN);
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if (list)
@@ -2377,6 +2378,8 @@ static int handle_revision_opt(struct rev_info *revs, int argc, const char **arg
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} else if ((argcount = parse_long_opt("until", argv, &optarg))) {
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revs->min_age = approxidate(optarg);
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return argcount;
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+ } else if (!strcmp(arg, "--maximal-only")) {
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+ revs->maximal_only = 1;
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} else if (!strcmp(arg, "--first-parent")) {
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revs->first_parent_only = 1;
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} else if (!strcmp(arg, "--exclude-first-parent-only")) {
@@ -3147,6 +3150,9 @@ int setup_revisions(int argc, const char **argv, struct rev_info *revs, struct s
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!!revs->reverse, "--reverse",
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!!revs->reflog_info, "--walk-reflogs");
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+ die_for_incompatible_opt2(!!revs->boundary, "--boundary",
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+ !!revs->maximal_only, "--maximal-only");
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+
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if (revs->no_walk && revs->graph)
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die(_("options '%s' and '%s' cannot be used together"), "--no-walk", "--graph");
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if (!revs->reflog_info && revs->grep_filter.use_reflog_filter)
@@ -4125,6 +4131,8 @@ enum commit_action get_commit_action(struct rev_info *revs, struct commit *commi
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{
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if (commit->object.flags & SHOWN)
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return commit_ignore;
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+ if (revs->maximal_only && (commit->object.flags & CHILD_VISITED))
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+ return commit_ignore;
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if (revs->unpacked && has_object_pack(revs->repo, &commit->object.oid))
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return commit_ignore;
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if (revs->no_kept_objects) {
revision.h
+4
-1
@@ -52,7 +52,9 @@
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#define NOT_USER_GIVEN (1u<<25)
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#define TRACK_LINEAR (1u<<26)
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#define ANCESTRY_PATH (1u<<27)
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-#define ALL_REV_FLAGS (((1u<<11)-1) | NOT_USER_GIVEN | TRACK_LINEAR | PULL_MERGE)
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+#define CHILD_VISITED (1u<<28)
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+#define ALL_REV_FLAGS (((1u<<11)-1) | NOT_USER_GIVEN | TRACK_LINEAR \
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+ | PULL_MERGE | CHILD_VISITED)
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#define DECORATE_SHORT_REFS 1
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#define DECORATE_FULL_REFS 2
@@ -189,6 +191,7 @@ struct rev_info {
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left_right:1,
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left_only:1,
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right_only:1,
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+ maximal_only:1,
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rewrite_parents:1,
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print_parents:1,
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show_decorations:1,
t/t6000-rev-list-misc.sh
+15
@@ -248,4 +248,19 @@ test_expect_success 'rev-list -z --boundary' '
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test_cmp expect actual
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'
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+test_expect_success 'rev-list --boundary incompatible with --maximal-only' '
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+ test_when_finished rm -rf repo &&
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+
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+ git init repo &&
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+ test_commit -C repo 1 &&
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+ test_commit -C repo 2 &&
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+
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+ oid1=$(git -C repo rev-parse HEAD~) &&
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+ oid2=$(git -C repo rev-parse HEAD) &&
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+
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+ test_must_fail git -C repo rev-list --boundary --maximal-only \
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+ HEAD~1..HEAD 2>err &&
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+ test_grep "cannot be used together" err
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+'
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+
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test_done
t/t6600-test-reach.sh
+75
@@ -762,4 +762,79 @@ test_expect_success 'for-each-ref is-base: --sort' '
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--sort=refname --sort=-is-base:commit-2-3
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'
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+test_expect_success 'rev-list --maximal-only (all positive)' '
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+ # Only one maximal.
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+ cat >input <<-\EOF &&
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+ refs/heads/commit-1-1
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+ refs/heads/commit-4-2
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+ refs/heads/commit-4-4
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+ refs/heads/commit-8-4
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+ EOF
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+
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+ cat >expect <<-EOF &&
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+ $(git rev-parse refs/heads/commit-8-4)
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+ EOF
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+ run_all_modes git rev-list --maximal-only --stdin &&
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+
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+ # All maximal.
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+ cat >input <<-\EOF &&
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+ refs/heads/commit-5-2
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+ refs/heads/commit-4-3
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+ refs/heads/commit-3-4
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+ refs/heads/commit-2-5
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+ EOF
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+
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+ cat >expect <<-EOF &&
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+ $(git rev-parse refs/heads/commit-5-2)
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+ $(git rev-parse refs/heads/commit-4-3)
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+ $(git rev-parse refs/heads/commit-3-4)
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+ $(git rev-parse refs/heads/commit-2-5)
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+ EOF
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+ run_all_modes git rev-list --maximal-only --stdin &&
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+
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+ # Mix of both.
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+ cat >input <<-\EOF &&
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+ refs/heads/commit-5-2
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+ refs/heads/commit-3-2
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+ refs/heads/commit-2-5
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+ EOF
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+
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+ cat >expect <<-EOF &&
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+ $(git rev-parse refs/heads/commit-5-2)
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+ $(git rev-parse refs/heads/commit-2-5)
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+ EOF
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+ run_all_modes git rev-list --maximal-only --stdin
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+'
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+
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+test_expect_success 'rev-list --maximal-only (range)' '
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+ cat >input <<-\EOF &&
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+ refs/heads/commit-1-1
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+ refs/heads/commit-2-5
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+ refs/heads/commit-6-4
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+ ^refs/heads/commit-4-5
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+ EOF
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+
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+ cat >expect <<-EOF &&
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+ $(git rev-parse refs/heads/commit-6-4)
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+ EOF
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+ run_all_modes git rev-list --maximal-only --stdin &&
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+
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+ # first-parent changes reachability: the first parent
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+ # reduces the second coordinate to 1 before reducing the
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+ # first coordinate.
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+ cat >input <<-\EOF &&
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+ refs/heads/commit-1-1
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+ refs/heads/commit-2-5
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+ refs/heads/commit-6-4
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+ ^refs/heads/commit-4-5
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+ EOF
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+
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+ cat >expect <<-EOF &&
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+ $(git rev-parse refs/heads/commit-6-4)
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+ $(git rev-parse refs/heads/commit-2-5)
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+ EOF
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+ run_all_modes git rev-list --maximal-only --stdin \
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+ --first-parent --exclude-first-parent-only
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+'
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+
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test_done