Rubén Justo wrote:
> Since 52d59cc645 (branch: add a --copy (-c) option to go with --move
> (-m), 2017-06-18) we can copy a branch to make a new branch with the
> '-c' (copy) option or to overwrite an existing branch using the '-C'
> (force copy) option. A no-op possibility is considered when we are
> asked to copy a branch to itself, to follow the same no-op introduced
> for the rename (-M) operation in 3f59481e33 (branch: allow a no-op
> "branch -M <current-branch> HEAD", 2011-11-25). To check for this, in
> 52d59cc645 we compared the branch names provided by the user, source
> (HEAD if omitted) and destination, and a match is considered as this
> no-op.
>
> Since ae5a6c3684 (checkout: implement "@{-N}" shortcut name for N-th
> last branch, 2009-01-17) a branch can be specified using shortcuts like
> @{-1}. This allows this usage:
>
> $ git checkout -b test
> $ git checkout -
> $ git branch -C test test # no-op
> $ git branch -C test @{-1} # oops
> $ git branch -C @{-1} test # oops
>
> As we are using the branch name provided by the user to do the
> comparison, if one of the branches is provided using a shortcut we are
> not going to have a match and a call to git_config_copy_section() will
> happen. This will make a duplicate of the configuration for that
> branch, and with this progression the second call will produce four
> copies of the configuration, and so on.
This is a clear explanation of what the issue is and why it's happening.
>
> Let's use the interpreted branch name instead for this comparison.
>
> The rename operation is not affected.
>
> Signed-off-by: Rubén Justo <rjusto@xxxxxxxxx>
> ---
> builtin/branch.c | 6 +++---
> t/t3204-branch-name-interpretation.sh | 10 ++++++++++
> 2 files changed, 13 insertions(+), 3 deletions(-)
>
> diff --git a/builtin/branch.c b/builtin/branch.c
> index 15be0c03ef..a35e174aae 100644
> --- a/builtin/branch.c
> +++ b/builtin/branch.c
> @@ -584,13 +584,13 @@ static void copy_or_rename_branch(const char *oldname, const char *newname, int
> strbuf_release(&logmsg);
>
> strbuf_addf(&oldsection, "branch.%s", interpreted_oldname);
> - strbuf_release(&oldref);
> strbuf_addf(&newsection, "branch.%s", interpreted_newname);
> - strbuf_release(&newref);
> if (!copy && git_config_rename_section(oldsection.buf, newsection.buf) < 0)
> die(_("Branch is renamed, but update of config-file failed"));
> - if (copy && strcmp(oldname, newname) && git_config_copy_section(oldsection.buf, newsection.buf) < 0)
> + if (copy && strcmp(interpreted_oldname, interpreted_newname) && git_config_copy_section(oldsection.buf, newsection.buf) < 0)
I double-checked that 'interpreted_oldname' and 'interpreted_newname' are
always set (and not only when a shortcut name is used), and they are. So,
this does exactly what you intend.
> die(_("Branch is copied, but update of config-file failed"));
> + strbuf_release(&oldref);
> + strbuf_release(&newref);
> strbuf_release(&oldsection);
> strbuf_release(&newsection);
> }
> diff --git a/t/t3204-branch-name-interpretation.sh b/t/t3204-branch-name-interpretation.sh
> index 793bf4d269..3399344f25 100755
> --- a/t/t3204-branch-name-interpretation.sh
> +++ b/t/t3204-branch-name-interpretation.sh
> @@ -57,6 +57,16 @@ test_expect_success 'create branch with pseudo-qualified name' '
> expect_branch refs/heads/refs/heads/qualified two
> '
>
> +test_expect_success 'force-copy a branch to itself via @{-1} is no-op' '
> + git branch -t copiable main &&
> + git checkout copiable &&
> + git checkout - &&
> + git branch -C @{-1} copiable &&
> + git config --get-all branch.copiable.merge >actual &&
> + echo refs/heads/main >expect &&
> + test_cmp expect actual
> +'
> +
And the test is straightforward and demonstrates the fix. Thanks for the
well-written patch, this looks good to me!
