--- a/mercurial/help/config.txt	Sun Jun 24 01:13:09 2018 -0400
+++ b/mercurial/help/config.txt	Sun Jul 02 00:32:09 2017 -0400
@@ -886,6 +886,12 @@
 of the hook in the config, respectively. In the example above, this will
 be ``$HG_HOOKTYPE=incoming`` and ``$HG_HOOKNAME=incoming.email``.
 
+.. container:: windows
+
+  Some basic Unix syntax is supported for portability, including ``$VAR``
+  and ``${VAR}`` style variables.  To use a literal ``$``, it must be
+  escaped with a back slash or inside of a strong quote.
+
 ``changegroup``
   Run after a changegroup has been added via push, pull or unbundle.  The ID of
   the first new changeset is in ``$HG_NODE`` and last is in ``$HG_NODE_LAST``.

--- a/mercurial/hook.py	Sun Jun 24 01:13:09 2018 -0400
+++ b/mercurial/hook.py	Sun Jul 02 00:32:09 2017 -0400
@@ -120,8 +120,6 @@
     return r, False
 
 def _exthook(ui, repo, htype, name, cmd, args, throw):
-    ui.note(_("running hook %s: %s\n") % (name, cmd))
-
     starttime = util.timer()
     env = {}
 
@@ -141,6 +139,12 @@
             v = stringutil.pprint(v)
         env['HG_' + k.upper()] = v
 
+    if pycompat.iswindows:
+        environ = procutil.shellenviron(env)
+        cmd = util.platform.shelltocmdexe(cmd, environ)
+
+    ui.note(_("running hook %s: %s\n") % (name, cmd))
+
     if repo:
         cwd = repo.root
     else:

--- a/tests/test-histedit-fold.t	Sun Jun 24 01:13:09 2018 -0400
+++ b/tests/test-histedit-fold.t	Sun Jul 02 00:32:09 2017 -0400
@@ -478,14 +478,7 @@
   1:199b6bb90248 b
   0:6c795aa153cb a
 
-Setup the proper environment variable symbol for the platform, to be subbed
-into the hook command.
-#if windows
-  $ NODE="%HG_NODE%"
-#else
-  $ NODE="\$HG_NODE"
-#endif
-  $ hg histedit 6c795aa153cb --config hooks.commit="echo commit $NODE" --commands - 2>&1 << EOF | fixbundle
+  $ hg histedit 6c795aa153cb --config hooks.commit='echo commit $HG_NODE' --commands - 2>&1 << EOF | fixbundle
   > pick 199b6bb90248 b
   > fold a1a953ffb4b0 c
   > pick 6c795aa153cb a
@@ -496,8 +489,24 @@
   1:9599899f62c0 a
   0:79b99e9c8e49 b
 
+Test unix -> windows style variable substitution in external hooks.
+
+  $ cat > $TESTTMP/tmp.hgrc <<'EOF'
+  > [hooks]
+  > pre-add = echo no variables
+  > post-add = echo ran $HG_ARGS, literal \$non-var, 'also $non-var', $HG_RESULT
+  > EOF
+
+TODO: Windows should output double quotes around "also $non-var"
   $ echo "foo" > amended.txt
-  $ hg add amended.txt
+  $ HGRCPATH=$TESTTMP/tmp.hgrc hg add -v amended.txt
+  running hook pre-add: echo no variables
+  no variables
+  adding amended.txt
+  running hook post-add: echo ran %HG_ARGS%, literal $non-var, 'also $non-var', %HG_RESULT% (windows !)
+  running hook post-add: echo ran $HG_ARGS, literal \$non-var, 'also $non-var', $HG_RESULT (no-windows !)
+  ran add -v amended.txt, literal $non-var, 'also $non-var', 0 (windows !)
+  ran add -v amended.txt, literal $non-var, also $non-var, 0 (no-windows !)
   $ hg ci -q --config extensions.largefiles= --amend -I amended.txt
   The fsmonitor extension is incompatible with the largefiles extension and has been disabled. (fsmonitor !)
 

--- a/tests/test-rebase-interruptions.t	Sun Jun 24 01:13:09 2018 -0400
+++ b/tests/test-rebase-interruptions.t	Sun Jul 02 00:32:09 2017 -0400
@@ -333,12 +333,7 @@
 
   $ cp -R a3 hook-pretxncommit
   $ cd hook-pretxncommit
-#if windows
-  $ NODE="%HG_NODE%"
-#else
-  $ NODE="\$HG_NODE"
-#endif
-  $ hg rebase --source 2 --dest 5 --tool internal:other --config "hooks.pretxncommit=hg log -r $NODE | grep \"summary:     C\""
+  $ hg rebase --source 2 --dest 5 --tool internal:other --config 'hooks.pretxncommit=hg log -r $HG_NODE | grep "summary:     C"'
   rebasing 2:965c486023db "C"
   summary:     C
   rebasing 6:a0b2430ebfb8 "F" (tip)