adopt-project.py: a source whose .git/refs/heads this user cannot read is refused source-default-branch-not-local with (its branches: none), a false list, where the refusal should name the directory git could not list #1219

Goal: a source whose .git/refs/heads this user cannot read is refused by name, source-unreadable naming that directory with the chmod cure, and never source-default-branch-not-local over a list of branches that is empty only because git could not list the directory.

Filed by lane openRepoShape-3, from RV1186's independent review of #1186 (#1151) at 07486a49 (#1186 issuecomment-6354299332), its follow-up under "An issue": .git/refs/heads at mode 000 (cloned: true) gives source-default-branch-not-local "(its branches: none)" "on main and at this head alike", "a false answer, outside #1151". It did not hold the landing: #1186 is READY and open at 07486a49, on milestone v1.2.1. RV1186's probe was uid 1000, git 2.43.0 and Python 3.12.3, with a stub gh and local remotes. Line numbers are main's at ef619c74. The defect is on main now, and #1186 does not touch it.

The branch list is asked once, and an empty answer is believed

State.

• _branch_names (adopt-project.py:3091) runs git for-each-ref --format=%(refname) <prefix> and returns what it prints. _default_branch (:2943) asks it for BRANCH_REFS (refs/heads/, :9673) at :2996, and Source._at (:2779) calls _default_branch (:2781) for every mode that opens a source.
• Where neither the default branch nor instead is in the list, _no_branch_of_its_own (:3007) raises source-default-branch-not-local, whose detail ends (its branches: <list>) through _branches_named (:4909, "none where there are none").
• Other callers ask git the same way and are as blind: _from_the_remote (:3044, _branch_names over ORIGIN_BRANCHES, refs/remotes/origin/, at :3053: where the branch is not there it says to ask origin again), _cloned_branch (:10316) and _branches_of (:4891, its own for-each-ref over both prefixes, behind _tracking_branch_problem, :4918).
• Nothing asks whether the directory could be listed. adopt-project.py: a --source, or a plan's source.local_path, with a part of its repository git reads at mode 000 (the .git, its HEAD, objects, refs or config, the git directory a gitdir: line names, or a directory above it) is refused source-unreadable naming that part, never git-failed and never cloned again (#1151) #1186's _refused_git_path, by its body (it is not on main), asks objects and refs, each searched, and no directory below refs.

What happens. RV1186, measured on main and at #1186's head: with .git/refs/heads at mode 000 and cloned: true, the run is source-default-branch-not-local with "(its branches: none)". The source has branches; the list is empty because git could not list the directory, which is the system's refusal and not the source's. The refusal's own advice, to check out a branch or to run plan with --tracking-branch naming one "the source has", then points away from the cure, a chmod. Read from the code (not measured), the same empty answer follows for refs/remotes/origin at mode 000 (_from_the_remote then says origin has no such branch either) and for a nested directory under refs/heads (a branch feature/x lives in refs/heads/feature).

Direction. Ask before believing an empty list, and refuse source-unreadable (the code at :1959 and _source_unreadable at :2045, both existing, with the permission cure), naming the directory this user cannot list. No new command and no flag.

• Ask by LISTING the directory, as git does, and not by a search (access(X_OK)), which is how adopt-project.py: a --source, or a plan's source.local_path, with a part of its repository git reads at mode 000 (the .git, its HEAD, objects, refs or config, the git directory a gitdir: line names, or a directory above it) is refused source-unreadable naming that part, never git-failed and never cloned again (#1151) #1186 asks objects and refs: a directory at mode --x can be searched and not listed. The writer measures mode 000 and --x first, and what for-each-ref does for each.

• Cover each directory git descends under refs/heads (a nested branch name) and refs/remotes/origin for _from_the_remote, or say in the PR why not.

• If adopt-project.py: a --source, or a plan's source.local_path, with a part of its repository git reads at mode 000 (the .git, its HEAD, objects, refs or config, the git directory a gitdir: line names, or a directory above it) is refused source-unreadable naming that part, never git-failed and never cloned again (#1151) #1186 has landed, the natural place is beside its _refused_git_path; if not, in _branch_names.

• The tests go in tests/test_adopt_tracking_branch.py, which already pins this refusal (NOT_LOCAL, :303, and its rows from :410), or in adopt-project.py: a --source, or a plan's source.local_path, with a part of its repository git reads at mode 000 (the .git, its HEAD, objects, refs or config, the git directory a gitdir: line names, or a directory above it) is refused source-unreadable naming that part, never git-failed and never cloned again (#1151) #1186's tests/test_adopt_unreadable_git_parts.py once that lands.

• A plan recording cloned: true over a source whose .git/refs/heads is at mode 000 (RV1186's case), under check and execute: REFUSED source-unreadable, exit 2, naming that directory, with the chmod cure, and not source-default-branch-not-local. The row fails before and passes after.

• plan --source over the same source: the same refusal.

• A nested directory under refs/heads at mode 000: the same, naming it.

• refs/remotes/origin at mode 000 where origin/HEAD names the branch: the same, and not "ask origin for its default branch again".

• A source that really has no branch of its own is still source-default-branch-not-local with (its branches: none): the file's existing rows pass unchanged.

• A readable source costs nothing new.

Related: #1186 and #1151 (the parts of a source's .git at mode 000), #1141 (the recorded source's .git itself), and #457 (the tracker for adopt-project.py, converting an existing repository in place).

Size: S.

Lane: openreposhape-3 (openRepoShape-3)