Adjust error reporting from merge failures and use LC_ALL=C for git (#8548)

There are two major components to this PR:

* This PR handles merge and rebase failures from merging a little more nicely with Flash errors rather a 500.
* All git commands are run in the LC_ALL="C" environment to ensure that error messages are in English. This DefaultLocale is defined in a way that if necessary (due to platform weirdness) it can be overridden at build time using LDFLAGS="-X "code.gitea.io/gitea/modules/git.DefaultLocale=C"" with C changed for the locale as necessary.

1 files changed, 30 insertions, 0 deletions

diff --git a/routers/repo/pull.go b/routers/repo/pull.go
index cb9c7c1164..0eea5fcbe6 100644
--- a/routers/repo/pull.go
+++ b/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