scripts: use last set tag if none given

Makes 'delta' and 'contributors.sh' easier to use.

Make the delta script invoke contrithanks to get current number of
contributors instead of counting THANKS, for accuracy.

Closes #4881

scripts/contributors.sh

@@ -6,7 +6,7 @@
 #                            | (__| |_| |  _ <| |___
 #                             \___|\___/|_| \_\_____|
 #
-# Copyright (C) 2013-2019, Daniel Stenberg, <daniel@haxx.se>, et al.
+# Copyright (C) 2013-2020, Daniel Stenberg, <daniel@haxx.se>, et al.
 #
 # This software is licensed as described in the file COPYING, which
 # you should have received as part of this distribution. The terms
@@ -29,10 +29,14 @@
 
 start=$1
 
-if test -z "$start"; then
+if test "$start" = "-h"; then
     echo "Usage: $0 <since this tag/hash> [--releasenotes]"
     exit
 fi
+if test -z "$start"; then
+    start=`git tag --sort=taggerdate | tail -1`;
+    echo "Since $start:"
+fi
 
 # filter out Author:, Commit: and *by: lines
 # cut off the email parts

scripts/delta

@@ -30,10 +30,14 @@
 
 $start = $ARGV[0];
 
-if($start eq "") {
+if($start eq "-h") {
     print "Usage: summary [tag]\n";
     exit;
 }
+elsif($start eq "") {
+    $start = `git tag --sort=taggerdate | tail -1`;
+    chomp $start;
+}
 
 $commits = `git log --oneline $start.. | wc -l`;
 $committers = `git shortlog -s $start.. | wc -l`;
@@ -45,8 +49,8 @@ $acommitters = `git shortlog -s | wc -l`;
 # delta from now compared to before
 $ncommitters = $acommitters - $bcommitters;
 
-# number of contributors right now (according to THANKS)
-$acontribs = `cat docs/THANKS | grep -c '^[^ ]'`;
+# number of contributors right now
+$acontribs = `./scripts/contrithanks.sh | grep -c '^[^ ]'`;
 # number when the tag tag was set
 $bcontribs = `git show $start:docs/THANKS | grep -c '^[^ ]'`;
 # delta
@@ -118,7 +122,7 @@ printf "Commit authors: %d out of which %d are new (out of %d)\n",
     $committers, $ncommitters, $acommitters;
 printf "Contributors in RELEASE-NOTES: %d\n",
     $numcontributors;
-printf "New contributors (in THANKS): %d (out of %d)\n",
+printf "New contributors: %d (out of %d)\n",
     $contribs, $acontribs;
 printf "New curl_easy_setopt() options: %d (out of %d)\n",
     $nsetopts, $asetopts;