Adjust error reporting from merge failures and use LC_ALL=C for git

models/error.go

@@ -1206,6 +1206,79 @@ func (err ErrInvalidMergeStyle) Error() string {
 		err.ID, err.Style)
 }
 
+// ErrMergeConflicts represents an error if merging fails with a conflict
+type ErrMergeConflicts struct {
+	Style  MergeStyle
+	StdOut string
+	StdErr string
+	Err    error
+}
+
+// IsErrMergeConflicts checks if an error is a ErrMergeConflicts.
+func IsErrMergeConflicts(err error) bool {
+	_, ok := err.(ErrMergeConflicts)
+	return ok
+}
+
+func (err ErrMergeConflicts) Error() string {
+	return fmt.Sprintf("Merge Conflict Error: %v: %s\n%s", err.Err, err.StdErr, err.StdOut)
+}
+
+// ErrMergeUnrelatedHistories represents an error if merging fails due to unrelated histories
+type ErrMergeUnrelatedHistories struct {
+	Style  MergeStyle
+	StdOut string
+	StdErr string
+	Err    error
+}
+
+// IsErrMergeUnrelatedHistories checks if an error is a ErrMergeUnrelatedHistories.
+func IsErrMergeUnrelatedHistories(err error) bool {
+	_, ok := err.(ErrMergeUnrelatedHistories)
+	return ok
+}
+
+func (err ErrMergeUnrelatedHistories) Error() string {
+	return fmt.Sprintf("Merge UnrelatedHistories Error: %v: %s\n%s", err.Err, err.StdErr, err.StdOut)
+}
+
+// ErrMergePushOutOfDate represents an error if merging fails due to unrelated histories
+type ErrMergePushOutOfDate struct {
+	Style  MergeStyle
+	StdOut string
+	StdErr string
+	Err    error
+}
+
+// IsErrMergePushOutOfDate checks if an error is a ErrMergePushOutOfDate.
+func IsErrMergePushOutOfDate(err error) bool {
+	_, ok := err.(ErrMergePushOutOfDate)
+	return ok
+}
+
+func (err ErrMergePushOutOfDate) Error() string {
+	return fmt.Sprintf("Merge PushOutOfDate Error: %v: %s\n%s", err.Err, err.StdErr, err.StdOut)
+}
+
+// ErrRebaseConflicts represents an error if rebase fails with a conflict
+type ErrRebaseConflicts struct {
+	Style     MergeStyle
+	CommitSHA string
+	StdOut    string
+	StdErr    string
+	Err       error
+}
+
+// IsErrRebaseConflicts checks if an error is a ErrRebaseConflicts.
+func IsErrRebaseConflicts(err error) bool {
+	_, ok := err.(ErrRebaseConflicts)
+	return ok
+}
+
+func (err ErrRebaseConflicts) Error() string {
+	return fmt.Sprintf("Rebase Error: %v: Whilst Rebasing: %s\n%s\n%s", err.Err, err.CommitSHA, err.StdErr, err.StdOut)
+}
+
 // _________                                       __
 // \_   ___ \  ____   _____   _____   ____   _____/  |_
 // /    \  \/ /  _ \ /     \ /     \_/ __ \ /    \   __\

modules/git/command.go

@@ -9,6 +9,7 @@ import (
 	"context"
 	"fmt"
 	"io"
+	"os"
 	"os/exec"
 	"strings"
 	"time"
@@ -24,10 +25,14 @@ var (
 	DefaultCommandExecutionTimeout = 60 * time.Second
 )
 
+// DefaultLocale is the default LC_ALL to run git commands in.
+const DefaultLocale = "C"
+
 // Command represents a command with its subcommands or arguments.
 type Command struct {
-	name string
-	args []string
+	name   string
+	args   []string
+	Locale string
 }
 
 func (c *Command) String() string {
@@ -43,8 +48,9 @@ func NewCommand(args ...string) *Command {
 	cargs := make([]string, len(GlobalCommandArgs))
 	copy(cargs, GlobalCommandArgs)
 	return &Command{
-		name: GitExecutable,
-		args: append(cargs, args...),
+		name:   GitExecutable,
+		args:   append(cargs, args...),
+		Locale: DefaultLocale,
 	}
 }
 
@@ -77,7 +83,12 @@ func (c *Command) RunInDirTimeoutEnvFullPipeline(env []string, timeout time.Dura
 	defer cancel()
 
 	cmd := exec.CommandContext(ctx, c.name, c.args...)
-	cmd.Env = env
+	if env == nil {
+		cmd.Env = append(os.Environ(), fmt.Sprintf("LC_ALL=%s", c.Locale))
+	} else {
+		cmd.Env = env
+		cmd.Env = append(cmd.Env, fmt.Sprintf("LC_ALL=%s", c.Locale))
+	}
 	cmd.Dir = dir
 	cmd.Stdout = stdout
 	cmd.Stderr = stderr

options/locale/locale_en-US.ini

@@ -1022,6 +1022,10 @@ pulls.rebase_merge_pull_request = Rebase and Merge
 pulls.rebase_merge_commit_pull_request = Rebase and Merge (--no-ff)
 pulls.squash_merge_pull_request = Squash and Merge
 pulls.invalid_merge_option = You cannot use this merge option for this pull request.
+pulls.merge_conflict = Merge Failed: There was a conflict whilst merging: %[1]s<br>%[2]s<br>Hint: Try a different strategy
+pulls.rebase_conflict = Merge Failed: There was a conflict whilst rebasing commit: %s[1]<br>%[1]s<br>%[2]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.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

@@ -626,6 +626,18 @@ func MergePullRequest(ctx *context.APIContext, form auth.MergePullRequestForm) {
 		if models.IsErrInvalidMergeStyle(err) {
 			ctx.Status(405)
 			return
+		} else if models.IsErrMergeConflicts(err) {
+			conflictError := err.(models.ErrMergeConflicts)
+			ctx.JSON(http.StatusConflict, conflictError)
+		} else if models.IsErrRebaseConflicts(err) {
+			conflictError := err.(models.ErrRebaseConflicts)
+			ctx.JSON(http.StatusConflict, conflictError)
+		} else if models.IsErrMergeUnrelatedHistories(err) {
+			conflictError := err.(models.ErrMergeUnrelatedHistories)
+			ctx.JSON(http.StatusConflict, conflictError)
+		} else if models.IsErrMergePushOutOfDate(err) {
+			ctx.Status(http.StatusConflict)
+			return
 		}
 		ctx.Error(500, "Merge", err)
 		return

routers/repo/pull.go

@@ -10,6 +10,7 @@ import (
 	"container/list"
 	"crypto/subtle"
 	"fmt"
+	"html"
 	"io"
 	"path"
 	"strings"
@@ -660,10 +661,39 @@ func MergePullRequest(ctx *context.Context, form auth.MergePullRequestForm) {
 	}
 
 	if err = pull_service.Merge(pr, ctx.User, ctx.Repo.GitRepo, models.MergeStyle(form.Do), message); err != nil {
+		sanitize := func(x string) string {
+			runes := []rune(x)
+
+			if len(runes) > 512 {
+				x = "..." + string(runes[len(runes)-512:])
+			}
+
+			return strings.Replace(html.EscapeString(x), "\n", "<br>", -1)
+		}
 		if models.IsErrInvalidMergeStyle(err) {
 			ctx.Flash.Error(ctx.Tr("repo.pulls.invalid_merge_option"))
 			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
 			return
+		} else if models.IsErrMergeConflicts(err) {
+			conflictError := err.(models.ErrMergeConflicts)
+			ctx.Flash.Error(ctx.Tr("repo.pulls.merge_conflict", sanitize(conflictError.StdErr), sanitize(conflictError.StdOut)))
+			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+			return
+		} else if models.IsErrRebaseConflicts(err) {
+			conflictError := err.(models.ErrRebaseConflicts)
+			ctx.Flash.Error(ctx.Tr("repo.pulls.rebase_conflict", sanitize(conflictError.CommitSHA), sanitize(conflictError.StdErr), sanitize(conflictError.StdOut)))
+			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+			return
+		} else if models.IsErrMergeUnrelatedHistories(err) {
+			log.Debug("MergeUnrelatedHistories error: %v", err)
+			ctx.Flash.Error(ctx.Tr("repo.pulls.unrelated_histories"))
+			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+			return
+		} else if models.IsErrMergePushOutOfDate(err) {
+			log.Debug("MergePushOutOfDate error: %v", err)
+			ctx.Flash.Error(ctx.Tr("repo.pulls.merge_out_of_date"))
+			ctx.Redirect(ctx.Repo.RepoLink + "/pulls/" + com.ToStr(pr.Index))
+			return
 		}
 		ctx.ServerError("Merge", err)
 		return