fix: tryFindGo doesn't trim repo path when absolute path is used (#4608)

When an absolute path is used like
`/home/christian/github.com/grafana/pyroscope/[....]`, we are not
matching the repository correctly and have to try quite a few files
before we truncated enough folders.

This change ensures that these cases are dealt with similar like a path
starting with the repo name.

Author: simonswine

pkg/frontend/vcs/source/find_go.go

@@ -112,8 +112,15 @@ func (ff FileFinder) tryFindGoFile(ctx context.Context, maxAttempts int) (*vcsv1
 	if maxAttempts <= 0 {
 		return nil, errors.New("invalid max attempts")
 	}
-	// Try to find the file in the repo.
-	path := strings.TrimPrefix(ff.path, strings.Join([]string{ff.repo.GetHostName(), ff.repo.GetOwnerName(), ff.repo.GetRepoName()}, "/"))
+
+	// trim repo path (e.g. "github.com/grafana/pyroscope/") in path
+	path := ff.path
+	repoPath := strings.Join([]string{ff.repo.GetHostName(), ff.repo.GetOwnerName(), ff.repo.GetRepoName(), ""}, "/")
+	if pos := strings.Index(path, repoPath); pos != -1 {
+		path = path[len(repoPath)+pos:]
+	}
+
+	// now try to find file in repo
 	path = strings.TrimLeft(path, "/")
 	attempts := 0
 	for {

pkg/frontend/vcs/source/find_go_test.go

@@ -57,7 +57,7 @@ func Test_tryFindGoFile(t *testing.T) {
 			expectedError:         nil,
 		},
 		{
-			name:                  "path with repository preffix",
+			name:                  "path with relative repository prefix",
 			searchedPath:          "github.com/grafana/pyroscope/main.go",
 			rootPath:              "",
 			repo:                  pyroscopeRepo,
@@ -66,6 +66,16 @@ func Test_tryFindGoFile(t *testing.T) {
 			expectedSearchedPaths: []string{"/main.go"},
 			expectedError:         nil,
 		},
+		{
+			name:                  "path with absolute repository prefix",
+			searchedPath:          "/Users/pyroscope/git/github.com/grafana/pyroscope/main.go",
+			rootPath:              "",
+			repo:                  pyroscopeRepo,
+			clientMock:            &VCSClientMock{fileToFind: "/main.go"},
+			attempts:              1,
+			expectedSearchedPaths: []string{"/main.go"},
+			expectedError:         nil,
+		},
 		{
 			name:                  "not found, attempts exceeded",
 			searchedPath:          "/var/service1/src/main.go",