fix(git): inject -- for bare-word-with-extension paths in git diff

[truffle-dev]

Closes #1669.

Reporter ran:

rtk git diff -- "package.json" "playwright.config.ts" ".harness/e2e_pipeline.yaml" "e2e-tests/config/loadEnv.ts" "e2e-tests/config/test.env"

and got fatal: bad revision 'package.json' while raw git diff -- ... worked.

What was happening

clap's trailing_var_arg = true drops -- when it's the first positional argument (existing comment at src/cmds/git/git.rs:74-83). normalize_diff_args (added for issue #1215) re-inserts it, walking the args until it finds the first one that looks path-like. Three rules existed before this PR:

1. Explicit prefix . or ~ → always a path.
2. Contains / or \ → use path_exists.
3. Bare word → never a path (added for issue rtk git diff produces empty output when branch name contains / #1431 to keep rtk git diff main resolving as a branch).

For the reporter's command, the first path-looking arg by rule 1 is .harness/e2e_pipeline.yaml at index 2. -- lands at index 2, leaving package.json (index 0) and playwright.config.ts (index 1) before the separator, where git treats them as revisions.

The fix

A new rule between the slash-path rule and the plain-bare-word rule: a bare word with a mid-string . (looks like a filename with extension) uses path_exists to distinguish real files from refs/tags.

if arg.find('.').is_some_and(|i| i > 0) {
    return path_exists(arg);
}

package.json and playwright.config.ts resolve as paths because the filesystem has them, so -- lands at index 0 instead of index 2. Plain bare words like main continue to be treated as refs even when a same-named file exists (issue #1431's deliberate behavior is preserved by the existing rule sitting after this one). A version-tag-shape arg like v1.2.3 that doesn't exist as a file remains a ref candidate.

Verification

Stash-bisect on a five-file repro that mirrors the reporter's exact command:

Before the patch:

$ rtk git diff -- "package.json" "playwright.config.ts" ".harness/e2e_pipeline.yaml" "e2e-tests/config/loadEnv.ts" "e2e-tests/config/test.env"
fatal: bad revision 'package.json'

After the patch:

$ rtk git diff -- "package.json" "playwright.config.ts" ".harness/e2e_pipeline.yaml" "e2e-tests/config/loadEnv.ts" "e2e-tests/config/test.env"
.harness/e2e_pipeline.yaml  | 2 +-
 e2e-tests/config/loadEnv.ts | 2 +-
 e2e-tests/config/test.env   | 2 +-
 package.json                | 2 +-
 playwright.config.ts        | 1 +
 5 files changed, 5 insertions(+), 4 deletions(-)

Tests

Four new unit tests next to the existing ones in mod tests:

• bare_word_with_extension_treated_as_path — single package.json that exists.
• bare_word_with_extension_no_injection_when_not_file — v1.2.3 tag pattern that doesn't exist on disk stays a ref.
• mixed_bare_extension_and_explicit_path — the reporter's exact five-file case.
• ref_before_bare_word_extension — ["HEAD", "Cargo.toml"] → ["HEAD", "--", "Cargo.toml"].

cargo test --release --bin rtk normalize_diff_args runs all 14 (10 prior + 4 new) green.

Scope notes

• run_log and run_show (src/cmds/git/git.rs:447, :240) do not call normalize_diff_args, so rtk git log -- file.json and rtk git show -- file.json likely have the same shape. Kept this PR narrow to the diff path the reporter hit; happy to extend the normalization to log/show in a follow-up if you prefer a sweep.
• The wshm AI-triage comment on the issue diagnosed this as "arg-forwarding bug ... arg splitting logic" at 95% confidence. The actual cause is more specific — the splitting works, but the rule for which leading args qualify as paths missed the bare-word-with-extension category.

[KuSh]

Hi, thanks for your PR, I'm willing to wait to see if clap allows us to keep escapes -- to allow transmitting it transparently. There seems to be traction outside our own needs.

[truffle-dev]

Sounds good. Subscribed to clap-rs/clap#5055. Happy to keep this rebased as a fallback, or close whenever you prefer.

[KuSh]

@truffle-dev After thinking more about this and seeing that clap's issue has not seen any updates since the spring of 2024, I pushed a more generic solution than stacking more heuristic on already existing ones, in #1823. If you want to give it a try, it would help, thanks

[truffle-dev]

Tried it. Built #1823, ran the args_utils tests (15/15 pass), and walked through the original cases:

• rtk cargo clippy -p test_pkg -- -D warnings — pass-through clean.
• rtk cargo test -- --nocapture — pass-through clean.
• rtk git diff -- existing.rs — -- survives.
• rtk git diff existing.rs — no -- injected, which is the deliberate scope cut.

Closing this in favor of #1823. The preserve-what-the-user-typed shape is cleaner than the path-existence heuristic; users who want a bare-word-with-extension treated as a path can still spell -- themselves, same as upstream git.

[truffle-dev]

Superseded by #1823.