MNT: Add update_changes script

Author: effigies

tools/update_changes.sh

@@ -0,0 +1,42 @@
+#!/bin/bash
+#
+# Collects the pull-requests since the latest release and
+# aranges them in the CHANGES.rst.txt file.
+#
+# This is a script to be run before releasing a new version.
+#
+# Usage /bin/bash update_changes.sh 1.0.1
+#
+
+# Setting      # $ help set
+set -u         # Treat unset variables as an error when substituting.
+set -x         # Print command traces before executing command.
+
+# Check whether the Upcoming release header is present
+head -1 CHANGES.rst | grep -q Upcoming
+UPCOMING=$?
+if [[ "$UPCOMING" == "0" ]]; then
+    head -n3  CHANGES.rst >> newchanges
+fi
+
+# Elaborate today's release header
+HEADER="$1 ($(date '+%B %d, %Y'))"
+echo $HEADER >> newchanges
+echo $( printf "%${#HEADER}s" | tr " " "=" ) >> newchanges
+echo "" >> newchanges
+
+# Search for PRs since previous release
+git log --grep="Merge pull request" `git describe --tags --abbrev=0`..HEAD --pretty='format:  * %b %s' | sed  's/Merge pull request \#\([^\d]*\)\ from\ .*/(\#\1)/' >> newchanges
+echo "" >> newchanges
+echo "" >> newchanges
+
+# Add back the Upcoming header if it was present
+if [[ "$UPCOMING" == "0" ]]; then
+    tail -n+4 CHANGES.rst >> newchanges
+else
+    cat CHANGES.rst >> newchanges
+fi
+
+# Replace old CHANGES.rst with new file
+mv newchanges CHANGES.rst
+