[BUG] shp build upload matches .gitignore patterns against the full path on disk #417

Is there an existing issue for this?

• I have searched the existing issues

Kubernetes Version

v1.32.2 (kind) and OpenShift on ROSA

Shipwright Version

Builds for OpenShift 1.9.0, and upstream Shipwright on kind. shp built from main @ a45e1612, and from #409.

Current Behavior

shp build upload checks each file against the .gitignore in the source folder. It passes the file's full path on disk to MatchesPath, for example /home/me/work/src/app/main.go. It should pass the path inside the source folder, main.go. This causes two problems.

1. A pattern that matches a parent folder drops every file. With src/ in .gitignore and the project at .../src/app, the upload is empty. The build then fails with DockerfileNotFound.
2. Patterns that start with / never match. /build and /dist should leave out those two top-level folders, but both are uploaded.

Expected Behavior

Patterns match the way git matches them, against the path relative to the folder that holds the .gitignore. src/ doesn't match anything above the source folder. /build leaves out build/ at the top, but keeps sub/build/.

Steps To Reproduce

1. Create a Build with source.type: Local and the buildah strategy.
2. Create a project at /tmp/src/app, with a Dockerfile and a .gitignore that contains src/.
3. Run shp build upload <build> /tmp/src/app --follow.
4. The build fails with DockerfileNotFound, because no files were uploaded.

To see the second problem, put /build in .gitignore and add a build/ folder. Its files appear in the build.

Anything else?

The fix is to pass the relative path to MatchesPath. #409 already computes it in skipPath.

relPath, err := filepath.Rel(t.src, fpath)
if err != nil {
	return false
}
relPath = filepath.ToSlash(relPath)
if strings.Contains("/"+relPath+"/", "/.git/") {
	return true
}
return t.gitIgnore != nil && t.gitIgnore.MatchesPath(relPath)

I tested this on OpenShift and on kind, with buildah and kaniko. Both problems went away, and sub/build/ was still uploaded. I can open a PR once #409 is merged.