doc: make links for hg role
The system has a bit of smartness:
:hg:`update` -> links to hg.1.html#update
:hg:`help diffs` -> links to hg.1.html#diffs
#!/bin/sh
mkdir t
cd t
hg init
echo a > a
hg add a
hg commit -m test
# do we ever miss a sub-second change?
for i in 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20; do
hg co -qC 0
echo b > a
hg st
done