fix(github): do not fail branch creation if it already exists

internal/client/github.go

@@ -2,6 +2,7 @@
 
 import (
 	"crypto/tls"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -231,7 +232,7 @@
 		},
 	)
 	if err != nil {
-		if res.StatusCode == 422 {
+		if res.StatusCode == http.StatusUnprocessableEntity {
 			log.WithError(err).Warn("pull request validation failed")
 			return nil
 		}
@@ -283,11 +284,11 @@
 
 	if defBranch != branch && branch != "" {
 		_, res, err := c.client.Repositories.GetBranch(ctx, repo.Owner, repo.Name, branch, 100)
-		if err != nil && (res == nil || res.StatusCode != 404) {
+		if err != nil && (res == nil || res.StatusCode != http.StatusNotFound) {
 			return fmt.Errorf("could not get branch %q: %w", branch, err)
 		}
 
-		if res.StatusCode == 404 {
+		if res.StatusCode == http.StatusNotFound {
 			defRef, _, err := c.client.Git.GetRef(ctx, repo.Owner, repo.Name, "refs/heads/"+defBranch)
 			if err != nil {
 				return fmt.Errorf("could not get ref %q: %w", "refs/heads/"+defBranch, err)
@@ -299,7 +300,10 @@
 					SHA: defRef.Object.SHA,
 				},
 			}); err != nil {
-				return fmt.Errorf("could not create ref %q from %q: %w", "refs/heads/"+branch, defRef.Object.GetSHA(), err)
+				rerr := new(github.ErrorResponse)
+				if !errors.As(err, &rerr) || rerr.Message != "Reference already exists" {
+					return fmt.Errorf("could not create ref %q from %q: %w", "refs/heads/"+branch, defRef.Object.GetSHA(), err)
+				}
 			}
 		}
 	}
@@ -313,7 +317,7 @@
 			Ref: branch,
 		},
 	)
-	if err != nil && (res == nil || res.StatusCode != 404) {
+	if err != nil && (res == nil || res.StatusCode != http.StatusNotFound) {
 		return fmt.Errorf("could not get %q: %w", path, err)
 	}
 
@@ -475,7 +479,7 @@
 	if err == nil {
 		return nil
 	}
-	if resp != nil && resp.StatusCode == 422 {
+	if resp != nil && resp.StatusCode == http.StatusUnprocessableEntity {
 		return err
 	}
 	return RetriableError{err}

internal/client/github_test.go

@@ -808,6 +808,68 @@ func TestGitHubCreateFileHappyPathUpdate(t *testing.T) {
 	require.NoError(t, client.CreateFile(ctx, config.CommitAuthor{}, repo, []byte("content"), "file.txt", "message"))
 }
 
+func TestGitHubCreateFileFeatureBranchAlreadyExists(t *testing.T) {
+	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		defer r.Body.Close()
+
+		if r.URL.Path == "/repos/someone/something/branches/feature" && r.Method == http.MethodGet {
+			w.WriteHeader(http.StatusNotFound)
+			return
+		}
+
+		if r.URL.Path == "/repos/someone/something/git/ref/heads/main" {
+			fmt.Fprint(w, `{"object": {"sha": "fake-sha"}}`)
+			return
+		}
+
+		if r.URL.Path == "/repos/someone/something/git/refs" && r.Method == http.MethodPost {
+			w.WriteHeader(http.StatusUnprocessableEntity)
+			fmt.Fprintf(w, `{"message": "Reference already exists"}`)
+			return
+		}
+
+		if r.URL.Path == "/repos/someone/something" {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprint(w, `{"default_branch": "main"}`)
+			return
+		}
+
+		if r.URL.Path == "/repos/someone/something/contents/file.txt" && r.Method == http.MethodGet {
+			w.WriteHeader(http.StatusNotFound)
+			return
+		}
+
+		if r.URL.Path == "/repos/someone/something/contents/file.txt" && r.Method == http.MethodPut {
+			w.WriteHeader(http.StatusOK)
+			return
+		}
+
+		if r.URL.Path == "/rate_limit" {
+			w.WriteHeader(http.StatusOK)
+			fmt.Fprint(w, `{"resources":{"core":{"remaining":120}}}`)
+			return
+		}
+
+		t.Error("unhandled request: " + r.Method + " " + r.URL.Path)
+	}))
+	defer srv.Close()
+
+	ctx := testctx.NewWithCfg(config.Project{
+		GitHubURLs: config.GitHubURLs{
+			API: srv.URL + "/",
+		},
+	})
+	client, err := newGitHub(ctx, "test-token")
+	require.NoError(t, err)
+	repo := Repo{
+		Owner:  "someone",
+		Name:   "something",
+		Branch: "feature",
+	}
+
+	require.NoError(t, client.CreateFile(ctx, config.CommitAuthor{}, repo, []byte("content"), "file.txt", "message"))
+}
+
 func TestGitHubCreateFileFeatureBranchDoesNotExist(t *testing.T) {
 	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		defer r.Body.Close()