Add support for upstream's tag signing commits, but adding the relevant files to autotools, and making those portable-compatible.

Allow the libexec helper, `got-read-patch` to be compiled, portably.

Make worktree_open part of the build.

Update portable to support changes for bloom, etc.

Allow for warnings via AM_CFLAGS in a common Makefile, and let those values propagate to all other Makefiles. Currently the more useful checks are disabled until upstream changes are made to reduce warnings. While here, also fix the version string to remove quotes.

libexec is a common path which is understood by autotools, and should be honoured. Patch from Christian "naddy" Weisgerber

This adds the capability to compile got-portable on FreeBSD.

When installing man pages, split out .1 and .5 as they install to different paths.

Rather than having a toplevel EXTRA_DIST target in the toplevel Makefile.am file, move the relevant files to their own Makefile.am locations.

The got_lib_privsep.h header expects the path to the libexec directory to be called GOT_LIBEXECDIR. At the moment it always falls back to using /usr/libexec. Fix what looks to be a typo.

This commit modifies the GoT main branch to be able to compile it under linux.