Handle push rejection message in Merge & Web Editor

models/error.go

@@ -7,6 +7,7 @@ package models
 
 import (
 	"fmt"
+	"strings"
 
 	"code.gitea.io/gitea/modules/git"
 )
@@ -1371,6 +1372,48 @@ func (err ErrMergePushOutOfDate) Error() string {
 	return fmt.Sprintf("Merge PushOutOfDate Error: %v: %s\n%s", err.Err, err.StdErr, err.StdOut)
 }
 
+// ErrPushRejected represents an error if merging fails due to unrelated histories
+type ErrPushRejected struct {
+	Style  MergeStyle
+	StdOut string
+	StdErr string
+	Err    error
+}
+
+// IsErrPushRejected checks if an error is a ErrPushRejected.
+func IsErrPushRejected(err error) bool {
+	_, ok := err.(ErrPushRejected)
+	return ok
+}
+
+func (err ErrPushRejected) Error() string {
+	return fmt.Sprintf("Merge PushRejected Error: %v: %s\n%s", err.Err, err.StdErr, err.StdOut)
+}
+
+// Message returns the cleaned message from Error
+func (err ErrPushRejected) Message() string {
+	messageBuilder := &strings.Builder{}
+	i := 0
+	for {
+		if len(err.StdErr) <= i+8 {
+			break
+		}
+		if err.StdErr[i:i+8] != "remote: " {
+			break
+		}
+		i = i + 8
+		nl := strings.IndexByte(err.StdErr[i:], '\n')
+		if nl > 0 {
+			messageBuilder.WriteString(err.StdErr[i : i+nl+1])
+			i = i + nl + 1
+		} else {
+			messageBuilder.WriteString(err.StdErr[i:])
+			i = len(err.StdErr)
+		}
+	}
+	return messageBuilder.String()
+}
+
 // ErrRebaseConflicts represents an error if rebase fails with a conflict
 type ErrRebaseConflicts struct {
 	Style     MergeStyle

options/locale/locale_en-US.ini

@@ -1086,6 +1086,7 @@ pulls.merge_conflict = Merge Failed: There was a conflict whilst merging: %[1]s<
 pulls.rebase_conflict = Merge Failed: There was a conflict whilst rebasing commit: %[1]s<br>%[2]s<br>%[3]s<br>Hint:Try a different strategy
 pulls.unrelated_histories = Merge Failed: The merge head and base do not share a common history. Hint: Try a different strategy
 pulls.merge_out_of_date = Merge Failed: Whilst generating the merge, the base was updated. Hint: Try again.
+pulls.push_rejected = Merge Failed: The push was rejected with the following message:<br>%s
 pulls.open_unmerged_pull_exists = `You cannot perform a reopen operation because there is a pending pull request (#%d) with identical properties.`
 pulls.status_checking = Some checks are pending
 pulls.status_checks_success = All checks were successful

routers/api/v1/repo/pull.go

@@ -684,6 +684,10 @@ func MergePullRequest(ctx *context.APIContext, form auth.MergePullRequestForm) {
 		} else if models.IsErrMergePushOutOfDate(err) {
 			ctx.Error(http.StatusConflict, "Merge", "merge push out of date")
 			return
+		} else if models.IsErrPushRejected(err) {
+			errPushRej := err.(models.ErrPushRejected)
+			ctx.Error(http.StatusConflict, "Merge", errPushRej.Message())
+			return
 		}
 		ctx.Error(http.StatusInternalServerError, "Merge", err)
 		return

routers/repo/pull.go

@@ -807,6 +807,12 @@ func MergePullRequest(ctx *context.Context, form auth.MergePullRequestForm) {
 			ctx.Flash.Error(ctx.Tr("repo.pulls.merge_out_of_date"))
 			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
 			return
+		} else if models.IsErrPushRejected(err) {
+			log.Debug("MergePushRejected error: %v", err)
+			pushrejErr := err.(models.ErrPushRejected)
+			ctx.Flash.Error(ctx.Tr("repo.pulls.push_rejected", pushrejErr.Message))
+			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+			return
 		}
 		ctx.ServerError("Merge", err)
 		return

services/pull/merge.go

@@ -392,6 +392,13 @@ func rawMerge(pr *models.PullRequest, doer *models.User, mergeStyle models.Merge
 				StdErr: errbuf.String(),
 				Err:    err,
 			}
+		} else if strings.Contains(errbuf.String(), "! [remote rejected]") {
+			return "", models.ErrPushRejected{
+				Style:  mergeStyle,
+				StdOut: outbuf.String(),
+				StdErr: errbuf.String(),
+				Err:    err,
+			}
 		}
 		return "", fmt.Errorf("git push: %s", errbuf.String())
 	}