mirrors/git
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

merge: allow to pretend a merge is made into a different branch

Browse Source 
When a series of patches for a topic-B depends on having topic-A,
the workflow to prepare the topic-B branch would look like this:

    $ git checkout -b topic-B main
    $ git merge --no-ff --no-edit topic-A
    $ git am <mbox-for-topic-B

When topic-A gets updated, recreating the first merge and rebasing
the rest of the topic-B, all on detached HEAD, is a useful
technique.  After updating topic-A with its new round of patches:

    $ git checkout topic-B
    $ prev=$(git rev-parse 'HEAD^{/^Merge branch .topic-A. into}')
    $ git checkout --detach $prev^1
    $ git merge --no-ff --no-edit topic-A
    $ git rebase --onto HEAD $prev @{-1}^0
    $ git checkout -B @{-1}

This will

 (0) check out the current topic-B.
 (1) find the previous merge of topic-A into topic-B.
 (2) detach the HEAD to the parent of the previous merge.
 (3) merge the updated topic-A to it.
 (4) reapply the patches to rebuild the rest of topic-B.
 (5) update topic-B with the result.

without contaminating the reflog of topic-B too much.  topic-B@{1}
is the "logically previous" state before topic-A got updated, for
example.  At (4), comparison (e.g. range-diff) between HEAD and
@{-1} is a meaningful way to sanity check the result, and the same
can be done at (5) by comparing topic-B and topic-B@{1}.

But there is one glitch.  The merge into the detached HEAD done in
the step (3) above gives us "Merge branch 'topic-A' into HEAD", and
does not say "into topic-B".

Teach the "--into-name=<branch>" option to "git merge" and its
underlying "git fmt-merge-message", to pretend as if we were merging
into <branch>, no matter what branch we are actually merging into,
when they prepare the merge message.  The pretend name honors the
usual "into <target>" suppression mechanism, which can be seen in
the tests added here.

Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Junio C Hamano
2021-12-20 14:53:43 -08:00
parent cd3e606211
commit bd2bc94252
7 changed files with 67 additions and 5 deletions
Download Patch File Download Diff File Expand all files Collapse all files

7
fmt-merge-msg.c
View File

@ -649,12 +649,15 @@ int fmt_merge_msg(struct strbuf *in, struct strbuf *out,
memset(&merge_parents, 0, sizeof(merge_parents));
/* get current branch */
/* learn the commit that we merge into and the current branch name */
current_branch = current_branch_to_free =
resolve_refdup("HEAD", RESOLVE_REF_READING, &head_oid, NULL);
if (!current_branch)
die("No current branch");
if (starts_with(current_branch, "refs/heads/"))
if (opts->into_name)
current_branch = opts->into_name;
else if (starts_with(current_branch, "refs/heads/"))
current_branch += 11;
find_merge_parents(&merge_parents, in, &head_oid);