makepkg: detect incorrect usage of provides array

Using > or < in the provides array is wrong so make it cause an error.
Fixes FS#12540.

Also, use bash substitution rather than spawning new processes where
possible in the error checking.  Move split package detection to a
better position.

Signed-off-by: Allan McRae <allan@archlinux.org>
[Dan: backport to maint]
Signed-off-by: Dan McGee <dan@archlinux.org>

doc/PKGBUILD.5.txt

@@ -160,7 +160,9 @@ name. The syntax is: `$$source=('filename::url')$$`
 	depend on 'cron' rather than 'dcron OR fcron'.
 	Versioned provisions are also possible, in the 'name=version' format.
 	For example, dcron can provide 'cron=2.0' to satisfy the 'cron>=2.0'
-	dependency of other packages.
+	dependency of other packages. Provisions involving the '>' and '<'
+	operators are invalid as only specifc versions of a package may be
+	provided.
 
 *replaces (array)*::
 	An array of packages that this package should replace, and can be used

scripts/makepkg.sh.in

@@ -1439,11 +1439,11 @@ if [ -z "$pkgrel" ]; then
 	error "$(gettext "%s is not allowed to be empty.")" "pkgrel"
 	exit 1
 fi
-if [ $(echo "$pkgver" | grep '-') ]; then
+if [ "$pkgver" != "${pkgver//-/}" ]; then
 	error "$(gettext "%s is not allowed to contain hyphens.")" "pkgver"
 	exit 1
 fi
-if [ $(echo "$pkgrel" | grep '-') ]; then
+if [ "$pkgrel" != "${pkgrel//-/}" ]; then
 	error "$(gettext "%s is not allowed to contain hyphens.")" "pkgrel"
 	exit 1
 fi
@@ -1465,6 +1465,14 @@ if ! in_array $CARCH ${arch[@]}; then
 	fi
 fi
 
+for provide in ${provides[@]}; do
+	if [ $provide != ${provide//</} -o $provide != ${provide//>/} ]; then
+		error "$(gettext "Provides array cannot contain comparison (< or >) operators.")"
+		exit 1
+	fi
+done
+unset provide
+
 if [ "$install" -a ! -f "$install" ]; then
 	error "$(gettext "Install scriptlet (%s) does not exist.")" "$install"
 	exit 1