magit--git-insert: Only return error if return-error is non-nil

Returning the Git error message causes many caller to signal a Lisp
error, which isn't what we want when we enable `magit-git-debug'.

1 files changed, 2 insertions, 1 deletions

diff --git a/lisp/magit-git.el b/lisp/magit-git.el
index 8bdd65d..b4b3200 100644
--- a/lisp/magit-git.el
+++ b/lisp/magit-git.el
@@ -565,7 +565,8 @@ insert the run command and stderr into the process buffer."
                       (errmsg (message "%s" errmsg))
                       ((zerop exit))
                       ((message "Git returned with exit-code %s" exit))))
-              (or errmsg exit))
+              (or (and return-error errmsg)
+                  exit))
           (ignore-errors (delete-file log))))
     (magit-process-git (list t nil) args)))