test-acl: alter sed construct to avoid changes in .hg/hgrc formatting

A future patch is going to add some extra commented-out boilerplate to
the top of .hg/hgrc during clone. In order to make this test not
require regular updates, switch to searching for [hooks] or [acl] and
print file from the first match to that pattern.

tests/test-acl.t

@@ -4,7 +4,7 b''
   >     shift
   >     echo "Pushing as user $user"
   >     echo 'hgrc = """'
-  >     sed -e 1,2d b/.hg/hgrc | grep -v fakegroups.py
+  >     sed -n '/\[[ha]/,$p' b/.hg/hgrc | grep -v fakegroups.py
   >     echo '"""'
   >     if test -f acl.config; then
   >         echo 'acl.config = """'
@@ -1122,6 +1122,8 b' fred is always allowed'
   $ do_push fred
   Pushing as user fred
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1197,6 +1199,8 b' no one is allowed inside foo/Bar/'
   $ do_push fred
   Pushing as user fred
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1278,6 +1282,8 b' OS-level groups'
   $ do_push fred
   Pushing as user fred
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1354,6 +1360,8 b' OS-level groups'
   $ do_push fred
   Pushing as user fred
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1476,6 +1484,8 b' No branch acls specified'
   $ do_push astro
   Pushing as user astro
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1558,6 +1568,8 b' Branch acl deny test'
   $ do_push astro
   Pushing as user astro
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1641,6 +1653,8 b' Branch acl empty allow test'
   $ do_push astro
   Pushing as user astro
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1718,6 +1732,8 b' Branch acl allow other'
   $ do_push astro
   Pushing as user astro
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1790,6 +1806,8 b' Branch acl allow other'
   $ do_push george
   Pushing as user george
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1878,6 +1896,8 b' push foobar into the remote'
   $ do_push george
   Pushing as user george
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -1965,6 +1985,8 b' Branch acl conflicting deny'
   $ do_push george
   Pushing as user george
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -2044,6 +2066,8 b" User 'astro' must not be denied"
   $ do_push astro
   Pushing as user astro
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]
@@ -2126,6 +2150,8 b' Non-astro users must be denied'
   $ do_push george
   Pushing as user george
   hgrc = """
+  [hooks]
+  pretxnchangegroup.acl = python:hgext.acl.hook
   [acl]
   sources = push
   [extensions]