Exit post-commit hook if no TSA is configured

instead of aborting commit.

hooks/post-commit

@@ -20,7 +20,10 @@
 #    
 #    The interactive user interfaces in modified source and object code versions
 #    of this program must display Appropriate Legal Notices, as required under
-#    Section 5 of the GNU Affero General Public License version 3.
+#    Section 5 of the GNU Affero General Public License version 3. In accordance
+#    with Section 7(b) of the GNU Affero General Public License, you must retain
+#    the Info line in every timestamp that is created or manipulated using a
+#    covered work.
 #    
 #    You can be released from the requirements of the license by purchasing
 #    a commercial license. Buying such a license is mandatory as soon as you
@@ -34,6 +37,12 @@
 #    address: info@mabulous.com
 #
 
+TSA0_URL=$(git config timestamping.tsa0.url)
+if [ -z "$TSA_URL" ]; then
+  # Do nothing if TSA0 has not been configured.
+  exit 0
+fi
+
 DIR="${BASH_SOURCE%/*}"
 if [[ ! -d "$DIR" ]]; then DIR="$PWD"; fi
 . "$DIR/timestamping"
@@ -71,12 +80,7 @@ while : ; do
   ((TSA_IDX++))
   TSA_URL=$(git config timestamping.tsa"$TSA_IDX".url)
   if [ -z "$TSA_URL" ]; then
-    if [ "$TSA_IDX" -eq 0 ]; then
-      echo_error "Error: no TSA url set. Define at least an url for TSA0 using git config timestamp.tsa0.url ... to set TSA URL".
-      exit 1
-    else
-      break
-    fi
+    break
   fi
   echo_info "for TSA $TSA_URL"
   TOKEN_OPTIONAL=$(git config --type=bool timestamping.tsa"$TSA_IDX".optional)
@@ -103,9 +107,10 @@ while : ; do
   fi
   #add token to commit message
   openssl ts -reply -token_in -in "$TOKEN_FILE" -token_out -text -out "$TMP_DIR"/token.txt &> "$OUT_STREAM"
+  #do not remove or change Info line (see license)
+  INFO="Info: Timestamp generated with GitTrustedTimestamps by Mabulous GmbH"
   TOKENBASE64=$(openssl base64 -in "$TOKEN_FILE")
   TOKENTEXT=$(cat "$TMP_DIR"/token.txt)
-  INFO="Info: Token digest is hash of parent commit."
   TRAILER_VALUE="$TSA_URL"$'\n'"$INFO"$'\n\n'"$TOKENTEXT"$'\n\n'"$TOKEN_HEADER"$'\n'"$TOKENBASE64"$'\n'"$TOKEN_FOOTER"
   #fold
   TRAILER_VALUE=$(echo -n "$TRAILER_VALUE" | sed -e 's/^/ /')