Update author listing script with support for several years

Did this months ago but never got to actually committing it...

.gitignore

@@ -1,2 +1,4 @@
 .doctrees
 *.mo
+authors.txt
+langs.txt

list-authors.sh

@@ -1,9 +1,6 @@
 #!/bin/bash
 
-set -euo pipefail
-IFS=$'\n\t'
-
-if [ -z "$1" ]; then
+if [ -z $1 ]; then
   echo "Pass a commit hash as argument to list authors between that commit and HEAD."
   exit 1
 fi
@@ -13,16 +10,22 @@ commit=$1
 rm -f authors.txt langs.txt
 
 for file in weblate/*.po; do
-  authors=$(git log "$commit"..HEAD --date=format:"%Y" --format="%aN <%aE>, %ad." "$file" | grep -v 'anonymous' | sort -u)
-  if [ -n "$authors" ]; then
+  authors=$(git log $commit..HEAD --date=format:"%Y" --format="%aN <%aE>, %ad." $file | grep -v 'anonymous' | sort -u)
+  if [ ! -z "$authors" ]; then
     new_authors=""
     while read -r author; do
-      found=$(grep "$author" "$file")
-      if [ -z "$found" ]; then
-         new_authors+=$author$'\n'
+      author_name=$(echo "$author" | sed 's/20[0-9][0-9].//')
+      author_year=$(echo "$author" | sed 's/.*\(20[0-9][0-9]\).*/\1/')
+      found_name=$(grep "$author_name" $file)
+      found_year=
+      if [ ! -z "$found_name" ]; then
+        found_year=$(grep "$author_year" <<< "$found_name")
+	  fi
+      if [ -z "$found_name" -o -z "$found_year" ]; then
+        new_authors+=$author$'\n'
       fi
     done <<< "$authors"
-    if [ -z "$new_authors" ]; then
+    if [ ! -z "$new_authors" ]; then
       echo "$file" >> langs.txt
       echo -e "\n* $file:\n" >> authors.txt
       echo "$new_authors" >> authors.txt