Invoke changelog_head from outside the pushd

so we know the relative path is right

release.sh

@@ -154,8 +154,9 @@ if [ $dodist -eq 0 ]; then
     # it's building
     DIST_VERSION="$tag" npm run dist
 
-    `dirname $0`/scripts/changelog_head.py > latest_changes.md
     popd
+
+    cat "${builddir}/CHANGELOG.md" | `dirname $0`/scripts/changelog_head.py > "${builddir}/latest_changes.md"
     for i in "$builddir"/dist/*; do
         assets="$assets -a $i"
         if [ -n "$signing_id" ]

scripts/changelog_head.py

@@ -1,13 +1,14 @@
 #!/usr/bin/env python
 
 """
-Outputs the body of the first entry of changelog file CHANGELOG.md
+Outputs the body of the first entry of changelog file on stdin
 """
 
 import re
+import sys
 
 found_first_header = False
-for line in open("CHANGELOG.md"):
+for line in sys.stdin:
     line = line.strip()
     if re.match(r"^Changes in \[.*\]", line):
         if found_first_header: