chore(build): add LOGFROM flag to check-pr rule

With this flag, the git log output is filtered to only include commits
from the specified commit to the current HEAD.

make check-pr                # from main (default)
make check-pr LOGFROM=v0.1.0 # from tag/branch
make check-pr LOGFROM=HEAD~1 # from commit
make check-pr LOGFROM=f3a4b2 # from commit

Makefile

@@ -858,6 +858,8 @@ check-err: \
 # pull request verifier
 #
 
+LOGFROM ?= main
+
 .PHONY: check-pr
 check-pr: \
 	check-fmt check-lint check-code \
@@ -868,7 +870,7 @@ check-pr: \
 	@echo
 
 	@$(CMD_GIT) \
-		log main..HEAD \
+		log $(LOGFROM)..HEAD \
 		--pretty=format:'%C(auto,yellow)%h%Creset **%C(auto,red)%s%Creset** _<sub>%C(auto,cyan)(%ad)%Creset %C(auto,green)%an \<%ae\>%Creset</sub>_%n%n```%n%b```%n' \
 		--date=format:"%Y/%b/%d"