builtin/stash: report failure to write to index
The git-stash(1) command needs to write to the index for many of its operations. When the index is locked by a concurrent writer it will thus fail to operate, which is expected. What is not expected though is that we do not print any error message at all in this case. The user can thus easily miss the fact that the command didn't do what they expected it to do and would be left wondering why that is. Fix this bug and report failures to write to the index. Add tests for the subcommands which hit the respective code paths. While at it, unify error messages when writing to the index fails. The chosen error message is already used in "builtin/stash.c". Reported-by: moti sd <motisd8@gmail.com> Signed-off-by: Patrick Steinhardt <ps@pks.im> Signed-off-by: Junio C Hamano <gitster@pobox.com>