Move hash_reqs.py from tools/ to scripts/lib/.

This is needed because hash_reqs.py is used to create a virtualenv.
Currently we only use virtualenv in development, but we will soon
start using it in production.  Scripts used in production should be
put in scripts/.

scripts/lib/hash_reqs.py

@@ -0,0 +1,71 @@
+#!/usr/bin/env python
+
+from __future__ import print_function
+
+import os
+import sys
+import argparse
+import hashlib
+
+if False:
+    from typing import Iterable, List, MutableSet
+
+def expand_reqs_helper(fpath, visited):
+    # type: (str, MutableSet[str]) -> List[str]
+    if fpath in visited:
+        return []
+    else:
+        visited.add(fpath)
+
+    curr_dir = os.path.dirname(fpath)
+    result = [] # type: List[str]
+
+    for line in open(fpath):
+        if line.startswith('#'):
+            continue
+        dep = line.split(" #", 1)[0].strip() # remove comments and strip whitespace
+        if dep:
+            if dep.startswith('-r'):
+                child = os.path.join(curr_dir, dep[3:])
+                result += expand_reqs_helper(child, visited)
+            else:
+                result.append(dep)
+    return result
+
+def expand_reqs(fpath):
+    # type: (str) -> List[str]
+    """
+    Returns a sorted list of unique dependencies specified by the requirements file `fpath`.
+    Removes comments from the output and recursively visits files specified inside `fpath`.
+    `fpath` can be either an absolute path or a relative path.
+    """
+    absfpath = os.path.abspath(fpath)
+    output = expand_reqs_helper(absfpath, set())
+    return sorted(set(output))
+
+def hash_deps(deps):
+    # type: (Iterable[str]) -> str
+    deps_str = "\n".join(deps) + "\n"
+    return hashlib.sha1(deps_str.encode('utf-8')).hexdigest()
+
+def main():
+    # type: () -> int
+    description = ("Finds the SHA1 hash of list of dependencies in a requirements file"
+                   " after recursively visiting all files specified in it.")
+    parser = argparse.ArgumentParser(description=description)
+    parser.add_argument("fpath", metavar="FILE",
+                        help="Path to requirements file")
+    parser.add_argument("--print", dest="print_reqs", action='store_true',
+                        help="Print all dependencies")
+    args = parser.parse_args()
+
+    deps = expand_reqs(args.fpath)
+    hash = hash_deps(deps)
+    print(hash)
+    if args.print_reqs:
+        for dep in deps:
+            print(dep)
+    return 0
+
+if __name__ == "__main__":
+    sys.exit(main())

scripts/lib/setup_venv.py

@@ -21,7 +21,7 @@ def setup_virtualenv(target_venv_path, requirements_file, virtualenv_args=None):
     # type: (str, str, List[str]) -> None
 
     # Check if a cached version already exists
-    path = os.path.join(ZULIP_PATH, 'tools', 'hash_reqs.py')
+    path = os.path.join(ZULIP_PATH, 'scripts', 'lib', 'hash_reqs.py')
     output = subprocess.check_output([path, requirements_file])
     sha1sum = output.split()[0]
     cached_venv_path = os.path.join(VENV_CACHE_PATH, sha1sum, os.path.basename(target_venv_path))