app-arch/tar: adapt pkg_postinst for prefix bootstrapping

This commit allows Portage to overwrite the binary executable
"tar" with a symbolic link, this situation is encountered during
Gentoo prefix bootstrap. If left unhandled, it causes the bootstrap
to fail with the error message:

    ln: failed to create symbolic link '/Users/ec2-user/gentoo/tmp/bin/tar': File exists

The original binary is renamed to tar.bak.

[sam: This is analogous to sys-devel/bison's hack too.]

Bug: https://bugs.gentoo.org/886123
Closes: https://bugs.gentoo.org/904887
Suggested-by: Sam James <[email protected]>
Signed-off-by: Yifeng Li <[email protected]>
Closes: gentoo#30723
Signed-off-by: Sam James <[email protected]>

app-arch/tar/tar-1.34-r2.ebuild

@@ -90,6 +90,13 @@ pkg_postinst() {
 	# ensure to preserve the symlink before app-alternatives/tar
 	# is installed
 	if [[ ! -h ${EROOT}/bin/tar ]]; then
+		if [[ -e ${EROOT}/usr/bin/tar ]] ; then
+			# bug #904887
+			ewarn "${EROOT}/usr/bin/tar exists but is not a symlink."
+			ewarn "This is expected during Prefix bootstrap and unsual otherwise."
+			ewarn "Moving away unexpected ${EROOT}/usr/bin/tar to .bak."
+			mv "${EROOT}/usr/bin/tar" "${EROOT}/usr/bin/tar.bak" || die
+		fi
 		ln -s gtar "${EROOT}/bin/tar" || die
 	fi
 }

app-arch/tar/tar-1.34-r3.ebuild

@@ -94,6 +94,13 @@ pkg_postinst() {
 	# ensure to preserve the symlink before app-alternatives/tar
 	# is installed
 	if [[ ! -h ${EROOT}/bin/tar ]]; then
+		if [[ -e ${EROOT}/usr/bin/tar ]] ; then
+			# bug #904887
+			ewarn "${EROOT}/usr/bin/tar exists but is not a symlink."
+			ewarn "This is expected during Prefix bootstrap and unsual otherwise."
+			ewarn "Moving away unexpected ${EROOT}/usr/bin/tar to .bak."
+			mv "${EROOT}/usr/bin/tar" "${EROOT}/usr/bin/tar.bak" || die
+		fi
 		ln -s gtar "${EROOT}/bin/tar" || die
 	fi
 }