has the syntax
rev 1.8 of src/bin/chmod/chmod.1
(the word "of" is optional)
or
src/bin/chmod/chmod.1 rev 1.7
'rev' and 'revision' are synonym.
If you close a PR you should now include the revision,
for example from PR 6055:
Fixed in src/gnu/usr.bin/as/config/obj-aout.c revision 1.6. [...]