Merge branch 'jk/config-cleanup' into maint-2.43
Code clean-up around use of configuration variables.
* jk/config-cleanup:
sequencer: simplify away extra git_config_string() call
gpg-interface: drop pointless config_error_nonbool() checks
push: drop confusing configset/callback redundancy
config: use git_config_string() for core.checkRoundTripEncoding
diff: give more detailed messages for bogus diff.* config
config: use config_error_nonbool() instead of custom messages
imap-send: don't use git_die_config() inside callback
git_xmerge_config(): prefer error() to die()
config: reject bogus values for core.checkstat