adopt-project.py check's throwaway repositories: a SHA-256 source, a tree path git refuses, a TMPDIR on another disk and this machine's hooks change the answers #910

Goal: check's throwaway repositories answer as the split will, or check says why they cannot, rather than stopping with git-failed or answering for another disk or another config.

Filed by lane openRepoShape-3, from its triage of #457 at the v1.1.1 release commit 5017830. It groups #457's lines L1-90, L1-92, L1-94 and L1-32, one pull request's worth.

State at 5017830. Read, not run.

• _SplitRehearsal (adopt-project.py check: a kept or moved file other than .gitattributes whose blob git add would re-encode passes, and execute ends adopt-lost or dies mounting the legs after both legs are pushed #654) makes its repository with tempfile.mkdtemp in TMPDIR (adopt-project.py:10160). It runs git init -q --template=<empty> there (:10177) with no --object-format.
• adopt-project.py: check finds, and execute refuses before any leg, a kept nested .gitattributes that outranks the root's line-ending rule for a pinned copy, and a root .gitattributes that git add would re-encode (#530) #619's probe repository is made the same way (:9614, :9628).
• Both run under _inherited_env() (:9551), which sets no core.hooksPath.
• _SymlinkProbe.symlinks catches only OSError (:9374).

What happens. Lane 1's review of #743 measured these on 78ffd729 merged with main b618ec16; no commit since names them.

• L1-90. check stops with REFUSED git-failed, exit 2, in the throwaway repository, where a finding belongs, in two cases:
  • a SHA-256 source, or GIT_DEFAULT_HASH=sha256 in the environment;
  • a tree path git refuses, such as .. or .Git/.
    Before adopt-project.py check: a kept or moved file other than .gitattributes whose blob git add would re-encode passes, and execute ends adopt-lost or dies mounting the legs after both legs are pushed #654, check passed both and execute failed after both leg remotes existed.
• L1-92. The rehearsal asks about case-sensitivity and symlinks where TMPDIR is. With TMPDIR on another file system than the work directory, it can answer differently from the split. Not measured.
• L1-94. A core.hooksPath hook from this machine's config, such as post-index-change, runs in both throwaway repositories: 12 runs against 2 on main in that review's probe.
• L1-32. Any failure of the symlink probe's git init other than an OSError stops check with "a git or gh command failed", where main printed the finding.

Direction.

• git init --object-format=<the source's>.
• Make a tree path git refuses a finding.
• Make the throwaway repositories in the work directory, or say where they are.
• Run them with -c core.hooksPath=<an empty directory>.
• Catch the probe's Refusal as the finding it stands for.

Size: M.

Lane: openreposhape-3 (openRepoShape-3)