Extract a single hash-like pattern from each line

Close #15

fzf-git.sh

@@ -180,7 +180,7 @@ _fzf_git_hashes() {
     --bind 'ctrl-d:execute:grep -o "[a-f0-9]\{7,\}" <<< {} | head -n 1 | xargs git diff > /dev/tty' \
     --color hl:underline,hl+:underline \
     --preview 'grep -o "[a-f0-9]\{7,\}" <<< {} | head -n 1 | xargs git show --color=always' "$@" |
-  grep -o "[a-f0-9]\{7,\}"
+  awk 'match($0, /[a-f0-9]{7,}/) { print substr($0, RSTART, RLENGTH) }'
 }
 
 _fzf_git_remotes() {