nhgitset version 4

To update, run "perl DEVEL/nhgitset.pl"

Fixes:
- "nhcommit -a" has been fixed
- NHDT was hardwired in places
- no longer complain about a missing dat directory outside of the
    NetHack source tree
- make update of gitinfo atomic
- Replace some hardwired directory separators with OS-dependent constructs

Backwards Incompatibilities:
- NH_DATESUB's DATE() is now Date() to match the other variables
- MSYS2 requires an additional Perl package - the MSYS2 docs have
    been updated

New Help System:
- git nhhelp
   This command mirrors "git help" for nh* commands.
- See git nhhelp nhsub for general help on substitution variables

New Substitution Variables:
-Brev()
    An aBREViation of $PREFIX-Branch$:$PREFIX-Revision$ - this
    may help get line length under control in file headers.
-Assert(TYPE=VALUE)
    If TYPE does not match VALUE, do not substitute on this line.
    TYPE P checks VALUE against nethack.substprefix
-Project(arg)
    Returns nethack.projectname if there is no arg and an uppercase
    version if arg is uc.

Other New Features:
- Add nethack.projectname
- Documentation updates - see "git nhhelp nhsub"
- On checkout or merge of a branch, check for nhgitset version updates
  and provide an optional message to the user.
- Move NH_DATESUB substitutions here from cron job to keep dates in sync
- PREFIX-* keywords now available in NH_DATESUB templates
- Support use of nhgitset.pl from a different repo; note that update
  checks will be dependent on keeping the original source repo up-to-date
  and in the same location.

doc/Guidebook.mn

@@ -1,4 +1,4 @@
-.\" $NHDT-Branch: NetHack-3.7 $:$NHDT-Revision: 1.574 $ $NHDT-Date: 1711040379 2024/03/21 16:59:39 $
+.\" $NHDT-Branch: keni-gitset $:$NHDT-Revision: 1.593 $ $NHDT-Date: 1730681007 2024/11/04 00:43:27 $
 .\"
 .\" This is an excerpt from the 'roff' man page from the 'groff' package.
 .\"+--
@@ -46,8 +46,8 @@
 .ds vr NetHack 3.7.0
 .ds f0 \*(vr
 .ds f1 \" empty
-.\"DO NOT REMOVE NH_DATESUB .ds f2 DATE(%B %-d, %Y)
-.ds f2 September 13, 2024
+.\"DO NOT REMOVE NH_DATESUB .ds f2 Date(%B %-d, %Y)
+.ds f2 November 4, 2024
 .
 .\" A note on some special characters:
 .\" \(lq = left double quote
@@ -6671,3 +6671,4 @@ Izchak Miller	Mike Stephenson
 .sm "Brand and product names are trademarks or registered trademarks \
 of their respective holders."
 .\"EOF
+changes