fix(cli): preserve password-only secret in flux create source git

`sourcesecret.buildGitSecret` previously wrote the Username and Password
secret fields only when *both* were set. With the Azure DevOps PAT flow,
`flux create source git --password=<pat>` has no username (the token is
the credential), so both fields were silently dropped and the resulting
secret was empty, breaking authentication.

Write the two fields independently, so:
- `--username` + `--password` -> username + password keys (unchanged);
- `--password` alone       -> password key only (fixes #3892);
- `--username` alone       -> username key only.

The SSH-passphrase case also becomes simpler: the duplicated
`if options.Password != ""` inside the keypair branch collapses into the
top-level write.

Adds a `buildGitSecret` unit test covering all four credential shapes,
including the Azure DevOps PAT scenario.

Closes #3892.

Signed-off-by: SAY-5 <SAY-5@users.noreply.github.com>

pkg/manifestgen/sourcesecret/sourcesecret.go

@@ -357,8 +357,14 @@ func buildGitSecret(keypair *ssh.KeyPair, hostKey []byte, options Options) (secr
 	secret.Labels = options.Labels
 	secret.StringData = map[string]string{}
 
-	if options.Username != "" && options.Password != "" {
+	// Username and Password are written independently so that callers can
+	// create a password-only secret (e.g. an Azure DevOps PAT, where the
+	// username is unused). When a keypair is also present, Password acts as
+	// the SSH private-key passphrase.
+	if options.Username != "" {
 		secret.StringData[UsernameSecretKey] = options.Username
+	}
+	if options.Password != "" {
 		secret.StringData[PasswordSecretKey] = options.Password
 	}
 	if options.BearerToken != "" {
@@ -374,10 +380,6 @@ func buildGitSecret(keypair *ssh.KeyPair, hostKey []byte, options Options) (secr
 		secret.StringData[PrivateKeySecretKey] = string(keypair.PrivateKey)
 		secret.StringData[PublicKeySecretKey] = string(keypair.PublicKey)
 		secret.StringData[KnownHostsSecretKey] = string(hostKey)
-		// set password if present
-		if options.Password != "" {
-			secret.StringData[PasswordSecretKey] = string(options.Password)
-		}
 	}
 
 	return secret

pkg/manifestgen/sourcesecret/sourcesecret_test.go

@@ -88,3 +88,67 @@ func Test_PasswordlessLoadKeyPair(t *testing.T) {
 		})
 	}
 }
+
+// Test_buildGitSecret_BasicAuthFields covers the regression reported in
+// https://github.com/fluxcd/flux2/issues/3892: providing just --password
+// (e.g. an Azure DevOps PAT, which ignores the username) must still
+// produce a secret containing the password field.
+func Test_buildGitSecret_BasicAuthFields(t *testing.T) {
+	tests := []struct {
+		name         string
+		opts         Options
+		wantUsername string
+		wantPassword string
+		wantHasUser  bool
+		wantHasPass  bool
+	}{
+		{
+			name:         "username and password",
+			opts:         Options{Username: "git", Password: "pw"},
+			wantUsername: "git",
+			wantPassword: "pw",
+			wantHasUser:  true,
+			wantHasPass:  true,
+		},
+		{
+			name:         "password only (Azure DevOps PAT)",
+			opts:         Options{Password: "pat-token"},
+			wantPassword: "pat-token",
+			wantHasUser:  false,
+			wantHasPass:  true,
+		},
+		{
+			name:         "username only",
+			opts:         Options{Username: "git"},
+			wantUsername: "git",
+			wantHasUser:  true,
+			wantHasPass:  false,
+		},
+		{
+			name:        "no credentials",
+			opts:        Options{},
+			wantHasUser: false,
+			wantHasPass: false,
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			secret := buildGitSecret(nil, nil, tt.opts)
+			gotUser, hasUser := secret.StringData[UsernameSecretKey]
+			gotPass, hasPass := secret.StringData[PasswordSecretKey]
+			if hasUser != tt.wantHasUser {
+				t.Errorf("username presence = %v, want %v", hasUser, tt.wantHasUser)
+			}
+			if hasPass != tt.wantHasPass {
+				t.Errorf("password presence = %v, want %v", hasPass, tt.wantHasPass)
+			}
+			if tt.wantHasUser && gotUser != tt.wantUsername {
+				t.Errorf("username = %q, want %q", gotUser, tt.wantUsername)
+			}
+			if tt.wantHasPass && gotPass != tt.wantPassword {
+				t.Errorf("password = %q, want %q", gotPass, tt.wantPassword)
+			}
+		})
+	}
+}