Merge branch 'maint'

* maint: (35 commits) config.c: guard config parser from value=NULL builtin-log.c: guard config parser from value=NULL imap-send.c: guard config parser from value=NULL wt-status.c: guard config parser from value=NULL setup.c: guard config parser from value=NULL remote.c: guard config parser from value=NULL merge-recursive.c: guard config parser from value=NULL http.c: guard config parser from value=NULL help.c: guard config parser from value=NULL git.c: guard config parser from value=NULL diff.c: guard config parser from value=NULL convert.c: guard config parser from value=NULL connect.c: guard config parser from value=NULL builtin-tag.c: guard config parser from value=NULL builtin-show-branch.c: guard config parser from value=NULL builtin-reflog.c: guard config parser from value=NULL builtin-log.c: guard config parser from value=NULL builtin-config.c: guard config parser from value=NULL builtin-commit.c: guard config parser from value=NULL builtin-branch.c: guard config parser from value=NULL ...