Editor error message misleading due to re-used key. (#29859)

The error message:

`editor.file_changed_while_editing = The file contents have changed
since you started editing. <a target="_blank" rel="noopener noreferrer"
href="%s">Click here</a> to see them or <strong>Commit Changes
again</strong> to overwrite them.`

Is re-used in inappropriate contexts. The link in the key goes to a 404
when the key is used in a situation where the file contents have not
changed.

Added two new keys to differentiate commit id mismatch and push out of
date conditions.

options/locale/locale_en-US.ini

@@ -1312,6 +1312,8 @@ editor.file_editing_no_longer_exists = The file being edited, "%s", no longer ex
 editor.file_deleting_no_longer_exists = The file being deleted, "%s", no longer exists in this repository.
 editor.file_changed_while_editing = The file contents have changed since you started editing. <a target="_blank" rel="noopener noreferrer" href="%s">Click here</a> to see them or <strong>Commit Changes again</strong> to overwrite them.
 editor.file_already_exists = A file named "%s" already exists in this repository.
+editor.commit_id_not_matching = The Commit ID does not match the ID when you began editing.  Commit into a patch branch and then merge.
+editor.push_out_of_date = The push appears to be out of date.
 editor.commit_empty_file_header = Commit an empty file
 editor.commit_empty_file_text = The file you're about to commit is empty. Proceed?
 editor.no_changes_to_show = There are no changes to show.

routers/web/repo/editor.go

@@ -333,9 +333,9 @@ func editFilePost(ctx *context.Context, form forms.EditRepoFileForm, isNewFile b
 				ctx.Error(http.StatusInternalServerError, err.Error())
 			}
 		} else if models.IsErrCommitIDDoesNotMatch(err) {
-			ctx.RenderWithErr(ctx.Tr("repo.editor.file_changed_while_editing", ctx.Repo.RepoLink+"/compare/"+util.PathEscapeSegments(form.LastCommit)+"..."+util.PathEscapeSegments(ctx.Repo.CommitID)), tplEditFile, &form)
+			ctx.RenderWithErr(ctx.Tr("repo.editor.commit_id_not_matching", ctx.Repo.RepoLink+"/compare/"+util.PathEscapeSegments(form.LastCommit)+"..."+util.PathEscapeSegments(ctx.Repo.CommitID)), tplEditFile, &form)
 		} else if git.IsErrPushOutOfDate(err) {
-			ctx.RenderWithErr(ctx.Tr("repo.editor.file_changed_while_editing", ctx.Repo.RepoLink+"/compare/"+util.PathEscapeSegments(form.LastCommit)+"..."+util.PathEscapeSegments(form.NewBranchName)), tplEditFile, &form)
+			ctx.RenderWithErr(ctx.Tr("repo.editor.push_out_of_date", ctx.Repo.RepoLink+"/compare/"+util.PathEscapeSegments(form.LastCommit)+"..."+util.PathEscapeSegments(form.NewBranchName)), tplEditFile, &form)
 		} else if git.IsErrPushRejected(err) {
 			errPushRej := err.(*git.ErrPushRejected)
 			if len(errPushRej.Message) == 0 {