fix(github): do not fail branch creation if it already exists (#4471)

github api is eventually consistent... so, we might ask for the branch,
it might say it does't exist, and when we try and create it, it might
error because it already exists.

this should avoid breaking it

---------

Signed-off-by: Carlos Alexandro Becker <caarlos0@users.noreply.github.com>

internal/client/github.go

@@ -2,6 +2,7 @@ package client
 
 import (
 	"crypto/tls"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
@@ -231,7 +232,7 @@ func (c *githubClient) OpenPullRequest(
 		},
 	)
 	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 @@ func (c *githubClient) CreateFile(
 
 	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 @@ func (c *githubClient) CreateFile(
 					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 @@ func (c *githubClient) CreateFile(
 			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 @@ func (c *githubClient) Upload(
 	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()