hash_reqs: Use combined package name and version to generate hash.

We were already using packages names along with their versions
to generate hash for the requirement file, as we were passing
the `.txt` files to the hash_reqs file instead of intended `.in` files
for which the functions in this file was originially designed.

Changed the expand_reqs_helper function to adapt for the `.txt` files.

scripts/lib/hash_reqs.py

@@ -6,25 +6,15 @@ import sys
 from typing import Iterable, List, MutableSet
 
 
-def expand_reqs_helper(fpath: str, visited: MutableSet[str]) -> List[str]:
-    if fpath in visited:
-        return []
-    else:
-        visited.add(fpath)
-
-    curr_dir = os.path.dirname(fpath)
+def expand_reqs_helper(fpath: str) -> List[str]:
     result = []  # type: List[str]
 
     for line in open(fpath):
-        if line.startswith('#'):
+        if line.strip().startswith(('#', '--hash')):
             continue
-        dep = line.split(" #", 1)[0].strip()  # remove comments and strip whitespace
+        dep = line.split(" \\", 1)[0].strip()
         if dep:
-            if dep.startswith('-r'):
-                child = os.path.join(curr_dir, dep[3:])
-                result += expand_reqs_helper(child, visited)
-            else:
-                result.append(dep)
+            result.append(dep)
     return result
 
 def expand_reqs(fpath: str) -> List[str]:
@@ -34,7 +24,7 @@ def expand_reqs(fpath: str) -> List[str]:
     `fpath` can be either an absolute path or a relative path.
     """
     absfpath = os.path.abspath(fpath)
-    output = expand_reqs_helper(absfpath, set())
+    output = expand_reqs_helper(absfpath)
     return sorted(set(output))
 
 def hash_deps(deps: Iterable[str]) -> str: