In the context of the new --rebase-merges mode, which was designed
specifically to allow for changing the existing branch topology
liberally, a user may want to extract commits into a completely fresh
branch that starts with a newly-created root commit.
This is now possible by inserting the command `reset [new root]` before
`pick`ing the commit that wants to become a root commit. Example:
reset [new root]
pick 012345 a commit that is about to become a root commit
pick 234567 this commit will have the previous one as parent
This does not conflict with other uses of the `reset` command because
`[new root]` is not (part of) a valid ref name: both the opening bracket
as well as the space are illegal in ref names.
Signed-off-by: Johannes Schindelin <johannes.schindelin@xxxxxx>
---
sequencer.c | 40 ++++++++++++++++++++++++++++------------
t/t3430-rebase-merges.sh | 34 ++++++++++++++++++++++++++++++++++
2 files changed, 62 insertions(+), 12 deletions(-)
diff --git a/sequencer.c b/sequencer.c
index 8eddda681d1..a7832399b1f 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -2747,18 +2747,34 @@ static int do_reset(const char *name, int len, struct replay_opts *opts)
if (hold_locked_index(&lock, LOCK_REPORT_ON_ERROR) < 0)
return -1;
- /* Determine the length of the label */
- for (i = 0; i < len; i++)
- if (isspace(name[i]))
- len = i;
-
- strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
- if (get_oid(ref_name.buf, &oid) &&
- get_oid(ref_name.buf + strlen("refs/rewritten/"), &oid)) {
- error(_("could not read '%s'"), ref_name.buf);
- rollback_lock_file(&lock);
- strbuf_release(&ref_name);
- return -1;
+ if (len == 10 && !strncmp("[new root]", name, len)) {
+ if (!opts->have_squash_onto) {
+ const char *hex;
+ if (commit_tree("", 0, the_hash_algo->empty_tree,
+ NULL, &opts->squash_onto,
+ NULL, NULL))
+ return error(_("writing fake root commit"));
+ opts->have_squash_onto = 1;
+ hex = oid_to_hex(&opts->squash_onto);
+ if (write_message(hex, strlen(hex),
+ rebase_path_squash_onto(), 0))
+ return error(_("writing squash-onto"));
+ }
+ oidcpy(&oid, &opts->squash_onto);
+ } else {
+ /* Determine the length of the label */
+ for (i = 0; i < len; i++)
+ if (isspace(name[i]))
+ len = i;
+
+ strbuf_addf(&ref_name, "refs/rewritten/%.*s", len, name);
+ if (get_oid(ref_name.buf, &oid) &&
+ get_oid(ref_name.buf + strlen("refs/rewritten/"), &oid)) {
+ error(_("could not read '%s'"), ref_name.buf);
+ rollback_lock_file(&lock);
+ strbuf_release(&ref_name);
+ return -1;
+ }
}
memset(&unpack_tree_opts, 0, sizeof(unpack_tree_opts));
diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
index 3d4dfdf7bec..35260862fcb 100755
--- a/t/t3430-rebase-merges.sh
+++ b/t/t3430-rebase-merges.sh
@@ -241,4 +241,38 @@ test_expect_success 'refuse to merge ancestors of HEAD' '
test_cmp_rev HEAD $before
'
+test_expect_success 'root commits' '
+ git checkout --orphan unrelated &&
+ (GIT_AUTHOR_NAME="Parsnip" GIT_AUTHOR_EMAIL="root@xxxxxxxxxxx" \
+ test_commit second-root) &&
+ test_commit third-root &&
+ cat >script-from-scratch <<-\EOF &&
+ pick third-root
+ label first-branch
+ reset [new root]
+ pick second-root
+ merge first-branch # Merge the 3rd root
+ EOF
+ test_config sequence.editor \""$PWD"/replace-editor.sh\" &&
+ test_tick &&
+ git rebase -i --force --root -r &&
+ test "Parsnip" = "$(git show -s --format=%an HEAD^)" &&
+ test $(git rev-parse second-root^0) != $(git rev-parse HEAD^) &&
+ test $(git rev-parse second-root:second-root.t) = \
+ $(git rev-parse HEAD^:second-root.t) &&
+ test_cmp_graph HEAD <<-\EOF &&
+ * Merge the 3rd root
+ |\
+ | * third-root
+ * second-root
+ EOF
+
+ : fast forward if possible &&
+ before="$(git rev-parse --verify HEAD)" &&
+ test_might_fail git config --unset sequence.editor &&
+ test_tick &&
+ git rebase -i --root -r &&
+ test_cmp_rev HEAD $before
+'
+
test_done
--
2.17.0.windows.1.38.g05ca542f78d
