Re: [PATCH 1/2] branch: force-copy a branch to itself via @{-1} is a no-op

> 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.
>
> Let's use the interpreted branch name instead for this comparison.
>
> The rename operation is not affected.

> @@ -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)

>  		die(_("Branch is copied, but update of config-file failed"));
> +	strbuf_release(&oldref);
> +	strbuf_release(&newref);
>  	strbuf_release(&oldsection);
>  	strbuf_release(&newsection);