Fix git_repository checkouts altered by host line-ending config

[rdesgroppes]

Description

The present fix proposes to pin both knobs for every git invocation in git_worker.bzl's _execute with both -c core.autocrlf=false and -c core.eol=lf.
A -c override outranks every config source (~/.gitconfig, /etc/gitconfig, $XDG_CONFIG_HOME/git/config, ...) and works on git 1.7.2+.

The checkout then reproduces the committed bytes:

• LF stays LF,
• an in-tree .gitattributes still wins so a repo keeping CRLF via eol=crlf is preserved,
• a CRLF blob is never stripped (the checkout path only ever adds CR, never removes it).

This is not neutralizing config sources:

• GIT_CONFIG_NOSYSTEM=1 would only drop /etc/gitconfig, not the user's ~/.gitconfig,
• GIT_CONFIG_GLOBAL and GIT_CONFIG_SYSTEM (set to /dev/null) need git 2.32+,
• worse, both of the above would wipe corresponding system-wide and user-specific configs, including environment-sensitive settings such as core.symlinks, credential.helper, http.proxy, etc.

The -c overrides touch only the two line-ending knobs.

There are 2 new black box tests that neutralize, in isolation, an injected host core.autocrlf (from $HOME/.gitconfig) and core.eol (from a GIT_CONFIG_SYSTEM file), asserting the checkout is byte-for-byte without shadowing corresponding in-tree .gitattributes settings.

Motivation

Fixes #30026.

git_repository and new_git_repository shell out to the system git, so their checkout inherits the host's git configuration. core.autocrlf and core.eol then rewrite line endings on checkout: with autocrlf=true (the Git for Windows default), a repository stored with LF is materialized with CRLF on one machine and LF on another, so a fetch is not reproducible and byte-sensitive rules break.

This pushes teams to fall back to http_archive, but that workaround doesn't of course apply to transitive bazel_deps.

Build API Changes

No

Checklist

• I have added tests for the new use cases (if any).
• I have updated the documentation (if applicable).

Release Notes

RELNOTES: git_repository and new_git_repository now check out files with the line endings stored in the repository, regardless of the host git configuration (core.autocrlf, core.eol).

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Updated for 0faabafe580979db81bda7b89985b68bb8965e2b