makepkg: make 'not a clone of' visible with a new error code

Add a new error code to expose the 'not a clone of' error state of some source
providers (git and fossil). This allows other tools integrating further and
handle this specific error state.

One usecase evolves around frequently changing source locations in PKGBUILDs
of packages in the AUR.

doc/makepkg.8.asciidoc

@@ -363,6 +363,10 @@ On exit, makepkg will return one of the following error codes.
 16::
 	Specified GPG key does not exist or failed to sign package.
 
+17::
+	The local repository is not a clone of the source repository
+	specified in PKGBUILD.
+
 See Also
 --------
 linkman:makepkg.conf[5], linkman:PKGBUILD[5], linkman:pacman[8]

scripts/libmakepkg/source/fossil.sh.in

@@ -24,6 +24,7 @@ LIBMAKEPKG_SOURCE_FOSSIL_SH=1
 
 MAKEPKG_LIBRARY=${MAKEPKG_LIBRARY:-'@libmakepkgdir@'}
 
+source "$MAKEPKG_LIBRARY/util/error.sh"
 source "$MAKEPKG_LIBRARY/util/message.sh"
 source "$MAKEPKG_LIBRARY/util/pkgbuild.sh"
 
@@ -57,7 +58,7 @@ download_fossil() {
 		if ! [[ $(fossil remote -R "$db") = "$url" ]]; then
 			error "$(gettext "%s is not a clone of %s")" "$db" "$url"
 			plainerr "$(gettext "Aborting...")"
-			exit 1
+			exit $E_NOT_A_CLONE_OF
 		fi
 		msg2 "$(gettext "Updating %s %s repo...")" "${repo}" "fossil"
 		if ! fossil pull -R "$db"; then

scripts/libmakepkg/source/git.sh.in

@@ -24,6 +24,7 @@ LIBMAKEPKG_SOURCE_GIT_SH=1
 
 MAKEPKG_LIBRARY=${MAKEPKG_LIBRARY:-'@libmakepkgdir@'}
 
+source "$MAKEPKG_LIBRARY/util/error.sh"
 source "$MAKEPKG_LIBRARY/util/message.sh"
 source "$MAKEPKG_LIBRARY/util/pkgbuild.sh"
 
@@ -60,7 +61,7 @@ download_git() {
 		if [[ "${url%%.git}" != "${remote_url%%.git}" ]] ; then
 			error "$(gettext "%s is not a clone of %s")" "$dir" "$url"
 			plainerr "$(gettext "Aborting...")"
-			exit 1
+			exit $E_NOT_A_CLONE_OF
 		fi
 		msg2 "$(gettext "Updating %s %s repo...")" "${repo}" "git"
 		if ! git fetch --all -p; then

scripts/libmakepkg/util/error.sh.in

@@ -39,3 +39,4 @@ E_ALREADY_BUILT=13
 E_INSTALL_FAILED=14
 E_MISSING_MAKEPKG_DEPS=15
 E_PRETTY_BAD_PRIVACY=16
+E_NOT_A_CLONE_OF=17