help: test if "hg help TOPIC" reference is valid
It's quite easy to make a reference invalid by mistake.
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/tests/test-check-help.t Wed Jan 25 22:39:17 2017 +0900
@@ -0,0 +1,25 @@
+#require test-repo
+
+ $ . "$TESTDIR/helpers-testrepo.sh"
+
+ $ cat <<'EOF' > scanhelptopics.py
+ > from __future__ import absolute_import, print_function
+ > import re
+ > import sys
+ > topics = set()
+ > topicre = re.compile(r':hg:`help ([a-z0-9\-.]+)`')
+ > for fname in sys.argv:
+ > with open(fname) as f:
+ > topics.update(m.group(1) for m in topicre.finditer(f.read()))
+ > for s in sorted(topics):
+ > print(s)
+ > EOF
+
+ $ cd "$TESTDIR"/..
+
+Check if ":hg:`help TOPIC`" is valid:
+(use "xargs -n1 -t" to see which help commands are executed)
+
+ $ hg files 'glob:{hgext,mercurial}/**/*.py' \
+ > | xargs python "$TESTTMP/scanhelptopics.py" \
+ > | xargs -n1 hg help > /dev/null