4.0.0: git_repository patch_cmds can no longer inspect git references

[dmivankov]

Description of the problem / feature request:

Using commands like patch_cmds = ["git ... origin/smth .. HEAD^"] worked in 3.3.1 but broke in 4.0.0

Error in fail: Error applying patch command git merge-base --is-ancestor HEAD^ HEAD:
fatal: Not a valid object name HEAD^

Bugs: what's the simplest, easiest way to reproduce this bug? Please provide a minimal example if possible.

WORKSPACE

load("@bazel_tools//tools/build_defs/repo:git.bzl", "git_repository")

git_repository(
    name = "skylib_git",
    commit = "f80bc733d4b9f83d427ce3442be2e07427b2cc8d",
    patch_cmds = [
        "git merge-base --is-ancestor origin/buildifier HEAD || true",  # more complex case that also used to work
        "git merge-base --is-ancestor HEAD^ HEAD"  # simpler case
    ],
    remote = "https://github.com/bazelbuild/bazel-skylib.git",
)

This was useful to make assertions on commits, like commit is successor (or ancestor) of certain branches. This isn't super important case (going away from git_repository to http_archive is said to be faster/more cacheable) but still a breaking change going from 3.3.1 to 4.0.0

What operating system are you running Bazel on?

NixOS

What's the output of bazel info release?

4.0.0

Any other information, logs, or outputs that you want to share?

#12455

[dmivankov]

Likely caused by #10137
and related to #8969
I'm not sure it qualifies as a non-breaking change

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