Fix rebase conflict detection in git 2.26 (#10930)

Git changed the technique used in rebase from
simple apply-patches to use merge. This breaks
our conflict detection code.

created by: Andrew Thornton <art27@cantab.net>

Co-authored-by: Lauris BH <lauris@nix.lv>

diff --git a/services/pull/merge.go b/services/pull/merge.go
index f9d9a27c9dc0dce4a72578f7a98f987914a108bf..b71784f00bf63a934610336caf49e0a85410efc3 100644 (file)
--- a/services/pull/merge.go
+++ b/services/pull/merge.go
@@ -211,17 +211,34 @@ func Merge(pr *models.PullRequest, doer *models.User, baseGitRepo *git.Repositor
                if err := git.NewCommand("rebase", baseBranch).RunInDirPipeline(tmpBasePath, &outbuf, &errbuf); err != nil {
                        // Rebase will leave a REBASE_HEAD file in .git if there is a conflict
                        if _, statErr := os.Stat(filepath.Join(tmpBasePath, ".git", "REBASE_HEAD")); statErr == nil {
-                               // The original commit SHA1 that is failing will be in .git/rebase-apply/original-commit
-                               commitShaBytes, readErr := ioutil.ReadFile(filepath.Join(tmpBasePath, ".git", "rebase-apply", "original-commit"))
-                               if readErr != nil {
-                                       // Abandon this attempt to handle the error
+                               var commitSha string
+                               ok := false
+                               failingCommitPaths := []string{
+                                       filepath.Join(tmpBasePath, ".git", "rebase-apply", "original-commit"), // Git < 2.26
+                                       filepath.Join(tmpBasePath, ".git", "rebase-merge", "stopped-sha"),     // Git >= 2.26
+                               }
+                               for _, failingCommitPath := range failingCommitPaths {
+                                       if _, statErr := os.Stat(filepath.Join(failingCommitPath)); statErr == nil {
+                                               commitShaBytes, readErr := ioutil.ReadFile(filepath.Join(failingCommitPath))
+                                               if readErr != nil {
+                                                       // Abandon this attempt to handle the error
+                                                       log.Error("git rebase staging on to base [%s:%s -> %s:%s]: %v\n%s\n%s", pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseRepo.FullName(), pr.BaseBranch, err, outbuf.String(), errbuf.String())
+                                                       return fmt.Errorf("git rebase staging on to base [%s:%s -> %s:%s]: %v\n%s\n%s", pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseRepo.FullName(), pr.BaseBranch, err, outbuf.String(), errbuf.String())
+                                               }
+                                               commitSha = strings.TrimSpace(string(commitShaBytes))
+                                               ok = true
+                                               break
+                                       }
+                               }
+                               if !ok {
+                                       log.Error("Unable to determine failing commit sha for this rebase message. Cannot cast as models.ErrRebaseConflicts.")
                                        log.Error("git rebase staging on to base [%s:%s -> %s:%s]: %v\n%s\n%s", pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseRepo.FullName(), pr.BaseBranch, err, outbuf.String(), errbuf.String())
                                        return fmt.Errorf("git rebase staging on to base [%s:%s -> %s:%s]: %v\n%s\n%s", pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseRepo.FullName(), pr.BaseBranch, err, outbuf.String(), errbuf.String())
                                }
-                               log.Debug("RebaseConflict at %s [%s:%s -> %s:%s]: %v\n%s\n%s", strings.TrimSpace(string(commitShaBytes)), pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseRepo.FullName(), pr.BaseBranch, err, outbuf.String(), errbuf.String())
+                               log.Debug("RebaseConflict at %s [%s:%s -> %s:%s]: %v\n%s\n%s", commitSha, pr.HeadRepo.FullName(), pr.HeadBranch, pr.BaseRepo.FullName(), pr.BaseBranch, err, outbuf.String(), errbuf.String())
                                return models.ErrRebaseConflicts{
                                        Style:     mergeStyle,
-                                       CommitSHA: strings.TrimSpace(string(commitShaBytes)),
+                                       CommitSHA: commitSha,
                                        StdOut:    outbuf.String(),
                                        StdErr:    errbuf.String(),
                                        Err:       err,