git archive-file: change base ARCHIVE_NAME (tj#1071)

Closes tj#1067

This makes the base ARCHIVE_NAME for `git-archive-file` to be the name
of the repo root directory instead of the name of the current directory.

bin/git-archive-file

@@ -1,11 +1,11 @@
 #!/usr/bin/env bash
 
 # extract current branch name
-BRANCH=$(git rev-parse --abbrev-ref HEAD 2> /dev/null)
+BRANCH=$(git rev-parse --abbrev-ref HEAD 2>/dev/null)
 
 # get name of the most top folder of current directory, used for the
 # output filename
-ARCHIVE_NAME=$(basename "$PWD")
+ARCHIVE_NAME=$(basename "$(git rev-parse --show-toplevel)")
 
 if [[ $BRANCH = tags* ]]; then
     BRANCH=$(git describe)