maint: make gen-contributors-list.sh suitable for generation of CREDITS

Implement various features in order to make it suitable for the
generation of the CREDITS file:
- add an option for including contributor e-mail;
- add an option to read additional list of contributors from stdin;
- add shorthand for referring to the initial commit of the branch;
- document all of the above in a help message.

* maint/gen-contributors-list.sh (print_help): New function.
(script): Rename to SCRIPT.
(SCRIPT_NORM_EMAILS, MATCH_OUT, OUT_EMAILS, OUT_NO_EMAILS, read_stdin,
include_email): New variables.
Add parsing of options, rewrite input processing.

Author: esyr

maint/gen-contributors-list.sh

@@ -24,16 +24,82 @@
 # (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 # THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
+print_help()
+{
+	cat <<__EOF__
+$0 [-h|--help] [-e|--include-email] [-|--stdin] [LAST_COMMIT [FIRST_COMMIT|--initial]]"
+
+Prints list of contributors for the specified range of commits.
+
+Options:
+  -h, --help    Print this message and exit.
+  -e, --include-email
+                Include e-mail address of each contributer in the output.
+  -, --stdin    Read the list of additional contributors from stdin.
+  LAST_COMMIT   Last commit of the range. Default value is HEAD.
+  FIRST_COMMIT  First commit in the range. Default is the last commit tagged
+                with a tag started with the character 'v'. If "--initial"
+                is specified, the first commit of the branch is used.
+__EOF__
+}
+
 get_commit_id()
 {
 	git rev-parse --verify "$1^{commit}"
 }
 
+SCRIPT='s/^[^:@<]\+:[[:space:]]*"\?\([^"<@[:space:]][^"<@]*\)"\?[[:space:]]\(<[^<@]\+@[^>]\+>\).*/\1 \2/p'
+# Script for adding angle brackets to e-mail addresses in case they are absent
+SCRIPT_NORM_EMAILS='s/[^[:space:]<@]\+@[^>]\+$/<\0>/'
+MATCH_OUT='^\([^<@[:space:]][^<@]*\)[[:space:]]\(<[^<@]\+@[^>]\+>\)$'
+OUT_EMAILS='\1 \2'
+OUT_NO_EMAILS='\1'
+
+read_stdin=0
+include_email=0
+
+while true; do
+	case "${1:-}" in
+	-h|--help)
+		print_help
+		exit 1
+		;;
+	-e|--include-email)
+		include_email=1
+		;;
+	-|--stdin)
+		read_stdin=1
+		;;
+	*)
+		break
+		;;
+	esac
+
+	shift
+done
+
 what="$(get_commit_id "${1:-@}")"
 since="${2:-$(git describe --abbrev=0 --match='v*' "$what")}"
-since="$(get_commit_id "$since")"
-script='s/^[^:@<]\+:[[:space:]]*\([^<@[:space:]][^<@]*\)[[:space:]]<[^<@]\+@.*/\1/p'
 
-git log --use-mailmap "^$since" "$what" |
-	sed -n "$script" |
-	LC_COLLATE=C sort -u
+case "$since" in
+--initial)
+	since="$(git rev-list --max-parents=0 $what)"
+	;;
+*)
+	since="$(get_commit_id "$since")"
+	;;
+esac
+
+if [ 0 = "$include_email" ]; then
+	out="$OUT_NO_EMAILS"
+else
+	out="$OUT_EMAILS"
+fi
+
+{
+	git log "^$since" "$what" | sed -n "$SCRIPT"
+	[ 0 = "$read_stdin" ] || sed "$SCRIPT_NORM_EMAILS"
+} \
+	| git check-mailmap --stdin \
+	| LC_COLLATE=C sort -u \
+	| sed "s/$MATCH_OUT/$out/"