Currently interpret_branch_name() takes either @{-N}, @{u}, or
some@{u} and returns an abbreviated refname, or a detached HEAD if
@{-N} resolves to such a state. Local branch names coming back for
@{-N} are returned as branch names without "refs/heads/", upstream
names coming back for @{u} are given after cleaning it up with
shorten_unambiguous_ref(). @{-N} resolved to a detached HEAD yields
a bare 40-HEX.
This makes the caller unnecessarily fragile. I started asking
(1) perhaps interpret_branch_name() can be updated to return a full
refname when it does return a ref;
(2) perhaps it can also be updated to say if its input @{-N} refers
to a detached HEAD state.
I looked at all existing callers of interpret_branch_name() to see
how feasible such a change is. Here is a preparatory analysis.
refs.c: substitute_branch_name()
The call to interpret_branch_name() by this function only wants to
see the branch name replaced to a full refname for the consumption
of dwim_ref() and dwim_log(), and does not want to see a detached
HEAD state at all.
Changing @{-N} that returns the bare branch name to return
refs/heads/$name is welcome. Changing $name@{u} that returns an
abbreviation to return a full refname is also welcome.
And we can error out early if @{-N} referred to a detached HEAD.
[answer: Yes/Yes]
revision.c: add_pending_object_with_mode()
The call to interpret_branch_name() by this function wants to turn
@{-N} and $name@{u} to a refname so that it can be passed to
add_reflog_for_walk(). Obviously it does not want to see a
detached state.
Again, this benefits if interpret_branch_name returned a full
refname, as add_reflog_for_walk() eventually ends up passing the
name to dwim_log().
[answer: Yes/Yes]
sha1_name.c: get_sha1_basic()
The call to interpret_branch_name() by this function wants to turn
@{-N} and $name@{u} to a string that can be fed to get_sha1_1() to
get an object name. Returning full refname or full object name is
a good change.
[answer: Yes/Yes]
sha1_name.c: interpret_branch_name()
@{-N}@{u} is first given to interpret_nth_prior_checkout() to turn
@{-N} into a branch name, and then appends @{u} to the result and
recursively call this function to expand $branch@{u}. Expansion
of @{-N} to full refname can break the second expansion, and needs
to be adjusted, but if @{-N} turns out to be a detaches state, we
would want to error out the resulting $HEX@{u} anyway, so updating
the API would result in a pair of real bug fixes.
[answer: Yes/Yes -- but this caller needs further adjustment]
sha1_name.c: strbuf_branchname()
The function wants to return an abbreviated branch name.
The callers of this function are:
builtin/branch.c: delete_branches()
"git branch -d -r master@{u}" may expand to "git branch -d -r
origin/master" and delete "refs/remotes/origin/master", and "git
branch -d @{-2}" would expand to "git branch -d next" and delete
"refs/heads/next".
strbuf_branchname() that returns a full refname would break
this caller and the caller needs to be updated to shorten
its output.
But if strbuf_branchname() can tell @{-N} were detached, we
can prevent removal of an unintended local branch.
builtin/checkout.c: setup_branch_path()
With the current code, "git checkout -b master@{u}" would
expand to "git checkout -b origin/master" and end up creating
"refs/heads/origin/master", which may not be a good thing.
strbuf_branchname() that returns a full refname would break
this caller and the caller needs to be updated to shorten
its output.
If strbuf_branchname() can tell @{-N} were detached, we can
error out instead of creating a bogus local branch.
builtin/merge.c: merge_name()
Uses strbuf_branchname() to turn @{-N} and $name@{u} into
something that can be fed to dwim_ref().
This does benefit if strbuf_branchname() can find out the
full refname.
If strbuf_branchname() can tell @{-N} were detached, we can
error out instead of creating a bogus local branch.
sha1_name.c: strbuf_check_branch_ref()
Used to see if the name is reasonable when appended to
refs/heads/.
strbuf_branchname() that returns a full refname would break
this caller and the caller needs to be updated to shorten
its output.
So strbuf_branchname() itself can tolerate an updated
interpret_branch_name() that returns full refname and it will
benefit if it can learn about detached state (many of its
callers would appreciate the latter).
[answer: Yes/Yes -- but this caller and its callers need some
adjustment].
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