`port selfupdate` fails when updating a local ports tree using `/usr/bin/git`

[halostatue (Austin Ziegler)]

When the git port is not installed, I have configuration in my .gitconfig that is not recognized by Apple’s default /usr/bin/git.

$ sudo port -v selfupdate
--->  Updating MacPorts base sources using rsync

Willkommen auf dem RSYNC-server auf ftp.fau.de.
Nicht all unsere Mirror sind per rsync verfuegbar.

Welcome to the RSYNC daemon on ftp.fau.de.
Not all of our mirrors are available through rsync.


receiving file list ... done
./

sent 66 bytes  received 98 bytes  109.33 bytes/sec
total size is 113716736  speedup is 693394.73
MacPorts base version 2.8.0 installed,
MacPorts base version 2.8.0 downloaded.
--->  Updating the ports tree
Synchronizing local ports tree from file:///Users/austin/ports
error: unsupported value for gpg.format: ssh
fatal: bad config variable 'gpg.format' in file '/Users/austin/.config/git/signatures' at line 3
Command failed: /usr/bin/git pull --rebase --autostash
Exit code: 128
Syncing local Git ports tree failed
Synchronizing local ports tree from rsync://rsync.macports.org/macports/release/tarballs/ports.tar

Willkommen auf dem RSYNC-server auf ftp.fau.de.
Nicht all unsere Mirror sind per rsync verfuegbar.

Welcome to the RSYNC daemon on ftp.fau.de.
Not all of our mirrors are available through rsync.


receiving file list ... done
./

sent 68 bytes  received 99 bytes  111.33 bytes/sec
total size is 100559872  speedup is 602154.92
Creating port index in /opt/local/var/macports/sources/rsync.macports.org/macports/release/tarballs/ports

Total number of ports parsed:	0
Ports successfully parsed:	0
Ports failed:			0
Up-to-date ports skipped:	29998

Error: Couldn't sync the ports tree: Synchronization of 1 source failed
Error: Follow https://guide.macports.org/#project.tickets if you believe there is a bug.
Error: /opt/local/bin/port: port selfupdate failed: Couldn't sync the ports tree: Synchronization of 1 source failed

The key error is bad config variable 'gpg.format'.

error: unsupported value for gpg.format: ssh
fatal: bad config variable 'gpg.format' in file '/Users/austin/.config/git/signatures' at line 3
Command failed: /usr/bin/git pull --rebase --autostash

This goes away when the git port is active, because it’s a modern version of git that supports SSH keys for signatures. It’s *possible* that this is fixed with macOS Ventura, but this should be documented at a minimum and it may be worth bundling a more recent version of git in available packages.