Fix update-release swallowing release source errors

When a release source returned a non-not-found error (e.g. a 401
auth failure), the error was discarded and replaced with a generic
"couldn't find X in any release source" message, giving no clue
about the real cause.

Wrap the underlying error so callers see the actual failure from
the release source (e.g. which source failed and why).

Closes #520

ai-assisted=yes

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: rizwanreza

internal/commands/update_release.go

@@ -79,10 +79,7 @@ func (u UpdateRelease) Execute(args []string) error {
 			GitHubRepository: releaseSpec.GitHubRepository,
 		}, false)
 		if err != nil {
-			if component.IsErrNotFound(err) {
-				return fmt.Errorf("error finding the release: %w", err)
-			}
-			return fmt.Errorf("couldn't find %q %s in any release source", u.Options.Name, u.Options.Version)
+			return fmt.Errorf("couldn't find %q %s in any release source: %w", u.Options.Name, u.Options.Version, err)
 		}
 
 		newVersion = remoteRelease.Version
@@ -98,10 +95,7 @@ func (u UpdateRelease) Execute(args []string) error {
 			GitHubRepository: releaseSpec.GitHubRepository,
 		})
 		if err != nil {
-			if component.IsErrNotFound(err) {
-				return fmt.Errorf("error finding the release: %w", err)
-			}
-			return fmt.Errorf("couldn't find %q %s in any release source", u.Options.Name, u.Options.Version)
+			return fmt.Errorf("couldn't find %q %s in any release source: %w", u.Options.Name, u.Options.Version, err)
 		}
 
 		localRelease, err = releaseSource.DownloadRelease(u.Options.ReleasesDir, remoteRelease)

internal/commands/update_release_test.go

@@ -342,6 +342,39 @@ var _ = Describe("UpdateRelease", func() {
 			})
 		})
 
+		When("a release source returns an unexpected error (e.g. auth failure) during GetMatchedRelease", func() {
+			BeforeEach(func() {
+				releaseSource.GetMatchedReleaseReturns(cargo.BOSHReleaseTarballLock{}, errors.New("401 Unauthorized"))
+			})
+
+			It("includes the underlying error in the returned error", func() {
+				err := updateReleaseCommand.Execute([]string{
+					"--kilnfile", "Kilnfile",
+					"--name", releaseName,
+					"--version", newReleaseVersion,
+					"--releases-directory", releasesDir,
+				})
+				Expect(err).To(MatchError(ContainSubstring("401 Unauthorized")))
+			})
+		})
+
+		When("a release source returns an unexpected error (e.g. auth failure) during FindReleaseVersion", func() {
+			BeforeEach(func() {
+				releaseSource.FindReleaseVersionReturns(cargo.BOSHReleaseTarballLock{}, errors.New("401 Unauthorized"))
+			})
+
+			It("includes the underlying error in the returned error", func() {
+				err := updateReleaseCommand.Execute([]string{
+					"--kilnfile", "Kilnfile",
+					"--name", releaseName,
+					"--version", newReleaseVersion,
+					"--releases-directory", releasesDir,
+					"--without-download",
+				})
+				Expect(err).To(MatchError(ContainSubstring("401 Unauthorized")))
+			})
+		})
+
 		When("downloading the release fails", func() {
 			BeforeEach(func() {
 				releaseSource.DownloadReleaseReturns(component.Local{}, errors.New("bad stuff"))