Running
git blame -L'/^static int make_script_with_merges/,/^}/' sequencer.c
tells me that the code range this patch touches and the function
whose feature this patch extends was mostly introduced in 1644c73c
(rebase-helper --make-script: introduce a flag to rebase merges,
2018-04-25) by Johannes Schindelin (CC'ed), so let's ask input from
him as an area expert.
Thanks.
"Nicolas Guichard via GitGitGadget" <gitgitgadget@xxxxxxxxx> writes:
> From: Nicolas Guichard <nicolas@xxxxxxxxxxx>
>
> When interactively rebasing merge commits, the commit message is parsed to
> extract a probably meaningful label name. For instance if the merge commit
> is “Merge branch 'feature0'”, then the rebase script will have thes lines:
> ```
> label feature0
>
> merge -C $sha feature0 # “Merge branch 'feature0'
> ```
>
> This heuristic fails in the case of octopus merges or when the merge commit
> message is actually unrelated to the parent commits.
>
> An example that combines both is:
> ```
> *---. 967bfa4 (HEAD -> integration) Integration
> |\ \ \
> | | | * 2135be1 (feature2, feat2) Feature 2
> | |_|/
> |/| |
> | | * c88b01a Feature 1
> | |/
> |/|
> | * 75f3139 (feat0) Feature 0
> |/
> * 25c86d0 (main) Initial commit
> ```
> yields the labels Integration, Integration-2 and Integration-3.
>
> Fix this by using a branch name for each merge commit's parent that is the
> tip of at least one branch, and falling back to a label derived from the
> merge commit message otherwise.
> In the example above, the labels become feat0, Integration and feature2.
>
> Signed-off-by: Nicolas Guichard <nicolas@xxxxxxxxxxx>
> ---
> sequencer.c | 25 +++++++++++++++++--------
> t/t3404-rebase-interactive.sh | 4 ++--
> t/t3430-rebase-merges.sh | 12 ++++++------
> 3 files changed, 25 insertions(+), 16 deletions(-)
>
> diff --git a/sequencer.c b/sequencer.c
> index e5eb6f8cd76..a092bd05692 100644
> --- a/sequencer.c
> +++ b/sequencer.c
> @@ -5833,7 +5833,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
> int root_with_onto = flags & TODO_LIST_ROOT_WITH_ONTO;
> int skipped_commit = 0;
> struct strbuf buf = STRBUF_INIT, oneline = STRBUF_INIT;
> - struct strbuf label = STRBUF_INIT;
> + struct strbuf label_from_message = STRBUF_INIT;
> struct commit_list *commits = NULL, **tail = &commits, *iter;
> struct commit_list *tips = NULL, **tips_tail = &tips;
> struct commit *commit;
> @@ -5856,6 +5856,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
> oidmap_init(&state.commit2label, 0);
> hashmap_init(&state.labels, labels_cmp, NULL, 0);
> strbuf_init(&state.buf, 32);
> + load_branch_decorations();
>
> if (revs->cmdline.nr && (revs->cmdline.rev[0].flags & BOTTOM)) {
> struct labels_entry *onto_label_entry;
> @@ -5916,18 +5917,18 @@ static int make_script_with_merges(struct pretty_print_context *pp,
> continue;
> }
>
> - /* Create a label */
> - strbuf_reset(&label);
> + /* Create a label from the commit message */
> + strbuf_reset(&label_from_message);
> if (skip_prefix(oneline.buf, "Merge ", &p1) &&
> (p1 = strchr(p1, '\'')) &&
> (p2 = strchr(++p1, '\'')))
> - strbuf_add(&label, p1, p2 - p1);
> + strbuf_add(&label_from_message, p1, p2 - p1);
> else if (skip_prefix(oneline.buf, "Merge pull request ",
> &p1) &&
> (p1 = strstr(p1, " from ")))
> - strbuf_addstr(&label, p1 + strlen(" from "));
> + strbuf_addstr(&label_from_message, p1 + strlen(" from "));
> else
> - strbuf_addbuf(&label, &oneline);
> + strbuf_addbuf(&label_from_message, &oneline);
>
> strbuf_reset(&buf);
> strbuf_addf(&buf, "%s -C %s",
> @@ -5935,6 +5936,14 @@ static int make_script_with_merges(struct pretty_print_context *pp,
>
> /* label the tips of merged branches */
> for (; to_merge; to_merge = to_merge->next) {
> + const char *label = label_from_message.buf;
> + const struct name_decoration *decoration =
> + get_name_decoration(&to_merge->item->object);
> +
> + if (decoration)
> + skip_prefix(decoration->name, "refs/heads/",
> + &label);
> +
> oid = &to_merge->item->object.oid;
> strbuf_addch(&buf, ' ');
>
> @@ -5947,7 +5956,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
> tips_tail = &commit_list_insert(to_merge->item,
> tips_tail)->next;
>
> - strbuf_addstr(&buf, label_oid(oid, label.buf, &state));
> + strbuf_addstr(&buf, label_oid(oid, label, &state));
> }
> strbuf_addf(&buf, " # %s", oneline.buf);
>
> @@ -6055,7 +6064,7 @@ static int make_script_with_merges(struct pretty_print_context *pp,
> free_commit_list(commits);
> free_commit_list(tips);
>
> - strbuf_release(&label);
> + strbuf_release(&label_from_message);
> strbuf_release(&oneline);
> strbuf_release(&buf);
>
> diff --git a/t/t3404-rebase-interactive.sh b/t/t3404-rebase-interactive.sh
> index f171af3061d..4896a801ee2 100755
> --- a/t/t3404-rebase-interactive.sh
> +++ b/t/t3404-rebase-interactive.sh
> @@ -1870,7 +1870,7 @@ test_expect_success '--update-refs adds commands with --rebase-merges' '
> pick $(git log -1 --format=%h branch2~1) F
> pick $(git log -1 --format=%h branch2) I
> update-ref refs/heads/branch2
> - label merge
> + label branch2
> reset onto
> pick $(git log -1 --format=%h refs/heads/second) J
> update-ref refs/heads/second
> @@ -1881,7 +1881,7 @@ test_expect_success '--update-refs adds commands with --rebase-merges' '
> update-ref refs/heads/third
> pick $(git log -1 --format=%h HEAD~2) M
> update-ref refs/heads/no-conflict-branch
> - merge -C $(git log -1 --format=%h HEAD~1) merge # merge
> + merge -C $(git log -1 --format=%h HEAD~1) branch2 # merge
> update-ref refs/heads/merge-branch
> EOF
>
> diff --git a/t/t3430-rebase-merges.sh b/t/t3430-rebase-merges.sh
> index 2aa8593f77a..cb891eeb5fd 100755
> --- a/t/t3430-rebase-merges.sh
> +++ b/t/t3430-rebase-merges.sh
> @@ -108,19 +108,19 @@ test_expect_success 'generate correct todo list' '
>
> reset onto
> pick $b B
> - label E
> + label first
>
> reset onto
> pick $c C
> label branch-point
> pick $f F
> pick $g G
> - label H
> + label second
>
> reset branch-point # C
> pick $d D
> - merge -C $e E # E
> - merge -C $h H # H
> + merge -C $e first # E
> + merge -C $h second # H
>
> EOF
>
> @@ -462,11 +462,11 @@ test_expect_success 'A root commit can be a cousin, treat it that way' '
> '
>
> test_expect_success 'labels that are object IDs are rewritten' '
> - git checkout -b third B &&
> + git checkout --detach B &&
> test_commit I &&
> third=$(git rev-parse HEAD) &&
> git checkout -b labels main &&
> - git merge --no-commit third &&
> + git merge --no-commit $third &&
> test_tick &&
> git commit -m "Merge commit '\''$third'\'' into labels" &&
> echo noop >script-from-scratch &&
