Allow mentioning tools paths in bindep

yum/dnf package managers do allow mentioning full path to executable
instead of rpm name for installing it.

This allows users to install needed tool regardless what package name
may provide it (which may depend on what repos they have installed or
enabled).

This allows 'package' names to start with slash as this is a requirement
for triggering this feature in yum/rpm.

Practice use-case scenario: user wants docker to be installed but docker
could be installed from docker rpm or from docker-ce rpm if user added
upstream repositories. Both of them provide the same executable, but
the package manager will pick one based on its priorities.

Command line example: yum install -y /usr/bin/docker

Change-Id: I7e47ee956e9496d9f47a98f9595790797c8d1789

bindep/depends.py

@@ -47,7 +47,7 @@ rule = <name>:name selector?:selector version?:version ('\n'|comment) -> (
     name, selector or [], version or [])
 lowercase = ('a'|'b'|'c'|'d'|'e'|'f'|'g'|'h'|'i'|'j'|'k'|'l'|'m'|'n'|'o'|'p'
             |'q'|'r'|'s'|'t'|'u'|'v'|'w'|'x'|'y'|'z')
-name = letterOrDigit:start (letterOrDigit|'.'|'+'|'-'|'_'|'/')+:rest
+name = (letterOrDigit|'/'):start (letterOrDigit|'.'|'+'|'-'|'_'|'/')+:rest
 ws = ' '+
 profile = ('!'?:neg <(lowercase|digit|':'|'-'|'.')+>:name) -> (neg!='!', name)
 profiles = '(' (ws? profile)*:p ws? ')' -> p

bindep/tests/test_depends.py

@@ -448,6 +448,15 @@ class TestDepends(TestCase):
             """))
         self.assertEqual(len(depends.active_rules(['default'])), 3)
 
+    def test_parser_accepts_full_path_to_tools(self):
+        # at least yum/dnf allow these instead of mentioning rpm names
+        depends = Depends(dedent("""\
+            /usr/bin/bash
+            """))
+        self.assertEqual(
+            [("/usr/bin/bash", [], [])],
+            depends.active_rules(["default"]))
+
     def test_parser_invalid(self):
         self.assertRaises(ometa.runtime.ParseError,
                           lambda: Depends("foo [platform:bar@baz]\n"))