extdata: use subprocess so we don't have to chdir() manually

mercurial/scmutil.py

@@ -13,6 +13,7 b' import hashlib'
 import os
 import re
 import socket
+import subprocess
 import weakref
 
 from .i18n import _
@@ -1038,20 +1039,18 b' def extdatasource(repo, source):'
         raise error.Abort(_("unknown extdata source '%s'") % source)
 
     data = {}
+    src = proc = None
+    try:
     if spec.startswith("shell:"):
         # external commands should be run relative to the repo root
         cmd = spec[6:]
-        cwd = os.getcwd()
-        os.chdir(repo.root)
-        try:
-            src = util.popen(cmd)
-        finally:
-            os.chdir(cwd)
+            proc = subprocess.Popen(cmd, shell=True, bufsize=-1,
+                                    close_fds=util.closefds,
+                                    stdout=subprocess.PIPE, cwd=repo.root)
+            src = proc.stdout
     else:
         # treat as a URL or file
         src = url.open(repo.ui, spec)
-
-    try:
         for l in src:
             if " " in l:
                 k, v = l.strip().split(" ", 1)
@@ -1064,6 +1063,9 b' def extdatasource(repo, source):'
             except (error.LookupError, error.RepoLookupError):
                 pass # we ignore data for nodes that don't exist locally
     finally:
+        if proc:
+            proc.communicate()
+        if src:
         src.close()
 
     return data