fix(coverage): detect branch on Travis CI push builds

[davehenton]

Fixes qltysh/cloud#8231.

Summary

Fix qlty coverage publish failing on Travis CI push builds (merge commits, direct pushes to a branch) with:

ERROR
> A branch, tag, or pull request must be specified.
> Please provide it using a supported CI provider or with one of
> --override-branch, --override-git-tag, or --override-pr-number

PR builds were unaffected — only push builds hit this.

The bug

TravisCI::branch() in qlty-coverage/src/ci/travisci.rs reads:

self.env
    .var("TRAVIS_PULL_REQUEST_BRANCH")
    .or_else(|| self.env.var("TRAVIS_BRANCH"))
    .unwrap_or_default()

On a Travis push build, TRAVIS_PULL_REQUEST_BRANCH is exported as an empty string, not unset. SystemEnv::var() is std::env::var(name).ok(), which returns Some("") for set-but-empty vars — so the Option is Some(""), .or_else(...) never fires, the TRAVIS_BRANCH fallback is skipped, and branch() returns "".

With an empty branch, empty pull_number() (it's "false" on push builds), and empty git_tag(), reference_type resolves to Unspecified and validation at qlty-cli/src/commands/coverage/utils.rs aborts the upload.

PR builds work because TRAVIS_PULL_REQUEST_BRANCH is populated with the source branch, so the Some("<branch>") path returns a valid value.

Reference: Travis default environment variables.

The fix

One-line change: filter out the empty string before falling through to TRAVIS_BRANCH.

 fn branch(&self) -> String {
     self.env
         .var("TRAVIS_PULL_REQUEST_BRANCH")
+        .filter(|b| !b.is_empty())
         .or_else(|| self.env.var("TRAVIS_BRANCH"))
         .unwrap_or_default()
 }

This mirrors the pattern the same file already uses in git_tag() for TRAVIS_TAG. PR builds keep working: TRAVIS_PULL_REQUEST_BRANCH is non-empty, the filter passes it through unchanged.

Testing

• Added branch_push_build_with_empty_pr_branch — sets TRAVIS_BRANCH=main, TRAVIS_PULL_REQUEST_BRANCH="", TRAVIS_PULL_REQUEST=false (exactly what Travis exports on a push build) and asserts branch() == "main".
• Reproduced the bug first: ran the new test against the unfixed code and confirmed it failed with left: "" right: "main" — matching the real-world error.
• Applied the fix, new test passes.
• Full qlty-coverage suite passes: 255/255 tests, 0 failures.
• Existing branch and branch_pull_request tests continue to pass, confirming no regression in the push-without-PR-var and PR-build codepaths.

[qltysh]

Coverage Impact - ubuntu-latest

This PR will not change total coverage.

Modified Files with Diff Coverage (1)

Rating	File	% Diff	Uncovered Line #s
	qlty-coverage/src/ci/travisci.rs	100.0%
	Total	100.0%

🚦 See full report on Qlty Cloud »

🛟 Help

• Diff Coverage: Coverage for added or modified lines of code (excludes deleted files). Learn more.

• Total Coverage: Coverage for the whole repository, calculated as the sum of all File Coverage. Learn more.

• File Coverage: Covered Lines divided by Covered Lines plus Missed Lines. (Excludes non-executable lines including blank lines and comments.)

  • Indirect Changes: Changes to File Coverage for files that were not modified in this PR. Learn more.

[qltysh]

Coverage Impact - macos-15

This PR will not change total coverage.

Modified Files with Diff Coverage (1)

Rating	File	% Diff	Uncovered Line #s
	qlty-coverage/src/ci/travisci.rs	100.0%
	Total	100.0%

🚦 See full report on Qlty Cloud »

🛟 Help

• Diff Coverage: Coverage for added or modified lines of code (excludes deleted files). Learn more.

• Total Coverage: Coverage for the whole repository, calculated as the sum of all File Coverage. Learn more.

• File Coverage: Covered Lines divided by Covered Lines plus Missed Lines. (Excludes non-executable lines including blank lines and comments.)

  • Indirect Changes: Changes to File Coverage for files that were not modified in this PR. Learn more.