AutoRevision: Fail earlier when the version tag is wrong

Start by checking that it matches the expected format and raise an error if it
doesn't. Don't replace all instances of "v" but just the first.

cmake/AutoRevision.cmake

@@ -70,9 +70,21 @@ endif()
 
 # Manipulate the tag so we can turn it into a list for use later
 string(STRIP "${FC21_REV_TAG}" FC21_REV_TAG)
-string(REPLACE "v" "" FC21_REV_TAG "${FC21_REV_TAG}")
+
+# Expected scheme:
+#  v3.0-dev
+#  v3.0-alpha.1
+#  v3.0-beta.1
+#  v3.0-rc.1
+#  v3.0
+#  v3.0.1
+if (NOT "${FC21_REV_TAG}"
+    MATCHES "^v[0-9]+\.[0-9]+(\.[0-9]+)?(-((((alpha)|(beta)|(rc))\.[0-9]+)|(dev)))?$")
+  message(SEND_ERROR "The version tag '${FC21_REV_TAG}' does not follow the expected format.")
+endif()
+
+string(SUBSTRING "${FC21_REV_TAG}" 1 -1 FC21_REV_TAG) # Remove initial v
 string(STRIP "${FC21_REV_TAG}" FC21_REV_TAG2)
-string(REPLACE "v" "" FC21_REV_TAG2 "${FC21_REV_TAG2}")
 string(REPLACE "." " " FC21_REV_TAG2 "${FC21_REV_TAG2}")
 string(REPLACE "-" " " FC21_REV_TAG2 "${FC21_REV_TAG2}")
 set(FC21_REV_TAG_LIST ${FC21_REV_TAG2})