--- a/.hgtags
+++ b/.hgtags
@@ -9,3 +9,4 @@ 0cbf9fd89672e73165e1bb4db1ec8f7f65b95c94
 07234759a3f750029ccaa001837d42fa12dd33ee 1.4
 77b22e5b4ea6c248e079afd0f1e544cb5690ce20 1.5
 d0f3a5c2cb56ce65d9ef1c611c8bfbebdc3bef34 1.5.1
+7d47a0f731354505ed9ae8d60d2a6996e8c3294f 1.6

--- a/hgsubversion/__init__.py
+++ b/hgsubversion/__init__.py
@@ -33,27 +33,9 @@ demandimport.ignore.extend([
     'svn.ra',
     ])
 
-try:
-    from mercurial import templatekw
-    # force demandimport to load templatekw
-    templatekw.keywords
-except ImportError:
-    templatekw = None
-
-try:
-    from mercurial import revset
-    # force demandimport to load revset
-    revset.methods
-except ImportError:
-    revset = None
-
-try:
-    from mercurial import subrepo
-    # require svnsubrepo and hg >= 1.7.1
-    subrepo.svnsubrepo
-    hgutil.checknlink
-except (ImportError, AttributeError), e:
-    subrepo = None
+from mercurial import templatekw
+from mercurial import revset
+from mercurial import subrepo
 
 import svncommands
 import util
@@ -124,9 +106,8 @@ except AttributeError:
 except ImportError:
     pass
 
-def extsetup():
+def extsetup(ui):
     """insert command wrappers for a bunch of commands"""
-    # add the ui argument to this function once we drop support for 1.3
 
     docvals = {'extension': 'hgsubversion'}
     for cmd, (generic, target, fixdoc, ppopts, opts) in wrapcmds.iteritems():
@@ -163,20 +144,13 @@ def extsetup():
          lambda: open(os.path.join(helpdir, 'subversion.rst')).read()),
     )
 
-    # in 1.6 and earler the help table is a tuple
-    if getattr(help.helptable, 'extend', None):
-        help.helptable.extend(entries)
-    else:
-        help.helptable = help.helptable + entries
+    help.helptable.extend(entries)
 
-    if templatekw:
-        templatekw.keywords.update(util.templatekeywords)
+    templatekw.keywords.update(util.templatekeywords)
 
-    if revset:
-        revset.symbols.update(util.revsets)
+    revset.symbols.update(util.revsets)
 
-    if subrepo:
-        subrepo.types['hgsubversion'] = svnexternals.svnsubrepo
+    subrepo.types['hgsubversion'] = svnexternals.svnsubrepo
 
 def reposetup(ui, repo):
     if repo.local():
@@ -184,7 +158,7 @@ def reposetup(ui, repo):
         for tunnel in ui.configlist('hgsubversion', 'tunnels'):
             hg.schemes['svn+' + tunnel] = svnrepo
 
-    if revset and ui.configbool('hgsubversion', 'nativerevs'):
+    if ui.configbool('hgsubversion', 'nativerevs'):
         extensions.wrapfunction(revset, 'stringset', util.revset_stringset)
 
 _old_local = hg.schemes['file']

--- a/hgsubversion/help/subversion.rst
+++ b/hgsubversion/help/subversion.rst
@@ -45,8 +45,8 @@ issue ``hg clone http://python-nose.goog
 works with any directory with a Subversion repository, and is known as a single
 directory clone. Normally, converted changesets will be marked as belonging to
 the ``default`` branch, but this can be changed by using the ``-b/--branch``
-option when using Mercurial 1.5 or later. To force single directory clone, use
-hgsubversion.layout option (see below for detailed help) ::
+option. To force single directory clone, use hgsubversion.layout option (see
+below for detailed help) ::
 
  $ hg clone --layout single svn+http://python-nose.googlecode.com/svn nose-hg
 
@@ -85,8 +85,6 @@ An example::
 
   $ hg log --template='{rev}:{node|short} {author|user}\nsvn: {svnrev}\n'
 
-The template keywords are available when using Mercurial 1.5 or later.
-
 For finding changesets from Subversion, hgsubversion extends revsets
 to provide two new selectors:
 
@@ -100,9 +98,7 @@ For example::
   $ hg log -r 'fromsvn()'
   $ hg log -r 'svnrev(500)'
 
-Revsets are available when using Mercurial 1.6 or later and are
-accepted by several Mercurial commands for specifying revisions. See
-``hg help revsets`` for details.
+See ``hg help revsets`` for details.
 
 Support for externals
 ---------------------
@@ -146,7 +142,7 @@ related Subversion repository.
 Alternatively, one can use the ``hgsubversion.externals`` in hgrc to
 specify ``subrepos`` as the externals mode. In this mode, ``.hgsub``
 and ``.hgsubstate`` files will be used instead of
-``.hgsvnexternals``. This feature requires Mercurial 1.7.1 or later.
+``.hgsvnexternals``.
 
 
 Using Subrepositories
@@ -183,8 +179,6 @@ with the revision identifier replaced wi
 
 This mode has the following limitations:
 
-* Require Mercurial >= 1.7.1 to work correctly on all platforms.
-
 * "hgsubversion" subrepositories require hgsubversion extension to be
   available. To operate transparently on ``svn:externals`` we have to
   stay as close as possible to their original property
@@ -365,10 +359,10 @@ settings:
     when necessary.
 
   ``hgsubversion.externals``
-    Set to ``subrepos`` to switch to subrepos-based externals support
-    (requires Mercurial 1.7.1 or later.) Default is ``svnexternals``,
-    which uses a custom hgsubversion-specific format and works on
-    older versions of Mercurial. Use ``ignore`` to avoid converting externals.
+    Set to ``subrepos`` to switch to subrepos-based externals support. Default
+    is ``svnexternals``, which uses a custom hgsubversion-specific format and
+    works on older versions of Mercurial. Use ``ignore`` to avoid converting
+    externals.
 
 The following options only have an effect on the initial clone of a repository:
 

--- a/hgsubversion/stupid.py
+++ b/hgsubversion/stupid.py
@@ -158,27 +158,8 @@ def filteriterhunks(meta):
         applycurrent = False
         # Passing False instead of textmode because we should never
         # be ignoring EOL type.
-        if iterhunks.func_code.co_argcount == 1:
-            # Since 1.9 (28762bb767dc)
-            fp = args[0]
-            gen = iterhunks(fp)
-        else:
-            ui, fp = args[:2]
-            if len(args) > 2:
-                sourcefile = args[2]
-            else:
-                sourcefile = kwargs.get('sourcefile', None)
-            if len(args) > 3:
-                textmode = args[3]
-            else:
-                textmode = kwargs.get('textmode', False)
-            if not iterhunks.func_defaults:
-                # Since 1.7 (cfedc529e4a1)
-                gen = iterhunks(ui, fp)
-            elif len(iterhunks.func_defaults) == 1:
-                gen = iterhunks(ui, fp, sourcefile)
-            else:
-                gen = iterhunks(ui, fp, sourcefile, textmode)
+        fp = args[0]
+        gen = iterhunks(fp)
         for data in gen:
             if data[0] == 'file':
                 if data[1][1] in meta.filemap:

--- a/hgsubversion/svnexternals.py
+++ b/hgsubversion/svnexternals.py
@@ -3,26 +3,14 @@ import cStringIO
 import os, re, shutil, stat, subprocess
 from mercurial import util as hgutil
 from mercurial.i18n import _
+from mercurial import subrepo
 
 try:
-    from mercurial import subrepo
-    # require svnsubrepo and hg >= 1.7.1
-    subrepo.svnsubrepo
-    hgutil.checknlink
-except (ImportError, AttributeError), e:
-    subrepo = None
-
-passpegrev = True # see svnsubrepo below
-try:
-    canonpath = hgutil.canonpath
+    from mercurial import scmutil
+    canonpath = scmutil.canonpath
 except (ImportError, AttributeError):
-    passpegrev = False
-    try:
-        from mercurial import scmutil
-        canonpath = scmutil.canonpath
-    except (ImportError, AttributeError):
-        from mercurial import pathutil
-        canonpath = pathutil.canonpath
+    from mercurial import pathutil
+    canonpath = pathutil.canonpath
 
 import util
 
@@ -398,58 +386,53 @@ def parse(ui, ctx):
         raise hgutil.Abort(_('unknown externals modes: %s') % mode)
     return external
 
-if subrepo:
-    class svnsubrepo(subrepo.svnsubrepo):
-        def __init__(self, ctx, path, state):
-            state = (state[0].split(':', 1)[1], state[1])
-            super(svnsubrepo, self).__init__(ctx, path, state)
-
-        def get(self, state, *args, **kwargs):
-            # Resolve source first
-            line = state[0].split(':', 1)[1]
-            source, pegrev = parsedefinition(line)[2:4]
-            try:
-                # Getting the root SVN repository URL is expensive.
-                # Assume the externals is absolute.
-                source = resolvesource(self._ui, None, source)
-            except RelativeSourceError:
-                svnurl = self._ctx._repo.ui.expandpath('default')
-                svnroot = getsvninfo(util.normalize_url(svnurl))[1]
-                source = resolvesource(self._ui, svnroot, source)
-            # hg < 1.9 svnsubrepo calls "svn checkout" with --rev
-            # only, so peg revisions are correctly used. 1.9 and
-            # higher, append the rev as a peg revision to the source
-            # URL, so we cannot add our own. We assume that "-r10
-            # url@2" will be similar to "url@10" most of the time.
-            if pegrev is not None and passpegrev:
-                source = source + '@' + pegrev
-            state = (source, state[1])
-            # hg-1.7.4-c19b9282d3a7 introduced the overwrite argument
-            return super(svnsubrepo, self).get(state, *args, **kwargs)
-
-        def dirty(self, ignoreupdate=False):
-            # You cannot compare anything with HEAD. Just accept it
-            # can be anything.
-            if hasattr(self, '_wcrevs'):
-                wcrevs = self._wcrevs()
-            else:
-                wcrev = self._wcrev()
-                wcrevs = (wcrev, wcrev)
-            if (('HEAD' in wcrevs or self._state[1] == 'HEAD' or
-                self._state[1] in wcrevs or ignoreupdate)
-                and not self._wcchanged()[0]):
-                return False
-            return True
-
-        def commit(self, text, user, date):
-            rev = super(svnsubrepo, self).commit(text, user, date)
-            # Keep unversioned externals unversioned
-            if self._state[1] == 'HEAD':
-                rev = 'HEAD'
-            return rev
-
-        def basestate(self):
-            # basestate() was introduced by bcb973abcc0b in 2.2
-            if self._state[1] == 'HEAD':
-                return 'HEAD'
-            return super(svnsubrepo, self).basestate()
+class svnsubrepo(subrepo.svnsubrepo):
+    def __init__(self, ctx, path, state):
+        state = (state[0].split(':', 1)[1], state[1])
+        super(svnsubrepo, self).__init__(ctx, path, state)
+
+    def get(self, state, *args, **kwargs):
+        # Resolve source first
+        line = state[0].split(':', 1)[1]
+        source, pegrev = parsedefinition(line)[2:4]
+        try:
+            # Getting the root SVN repository URL is expensive.
+            # Assume the externals is absolute.
+            source = resolvesource(self._ui, None, source)
+        except RelativeSourceError:
+            svnurl = self._ctx._repo.ui.expandpath('default')
+            svnroot = getsvninfo(util.normalize_url(svnurl))[1]
+            source = resolvesource(self._ui, svnroot, source)
+        # hg 1.9 and higher, append the rev as a peg revision to
+        # the source URL, so we cannot add our own. We assume
+        # that "-r10 url@2" will be similar to "url@10" most of
+        # the time.
+        state = (source, state[1])
+        return super(svnsubrepo, self).get(state, *args, **kwargs)
+
+    def dirty(self, ignoreupdate=False):
+        # You cannot compare anything with HEAD. Just accept it
+        # can be anything.
+        if hasattr(self, '_wcrevs'):
+            wcrevs = self._wcrevs()
+        else:
+            wcrev = self._wcrev()
+            wcrevs = (wcrev, wcrev)
+        if (('HEAD' in wcrevs or self._state[1] == 'HEAD' or
+            self._state[1] in wcrevs or ignoreupdate)
+            and not self._wcchanged()[0]):
+            return False
+        return True
+
+    def commit(self, text, user, date):
+        rev = super(svnsubrepo, self).commit(text, user, date)
+        # Keep unversioned externals unversioned
+        if self._state[1] == 'HEAD':
+            rev = 'HEAD'
+        return rev
+
+    def basestate(self):
+        # basestate() was introduced by bcb973abcc0b in 2.2
+        if self._state[1] == 'HEAD':
+            return 'HEAD'
+        return super(svnsubrepo, self).basestate()

--- a/hgsubversion/svnrepo.py
+++ b/hgsubversion/svnrepo.py
@@ -71,10 +71,6 @@ def generate_repo_class(ui, repo):
         """
         original = getattr(repo, fn.__name__, None)
 
-        # remove when dropping support for hg < 1.6.
-        if original is None and fn.__name__ == 'findoutgoing':
-            return
-
         def wrapper(self, *args, **opts):
             capable = getattr(args[0], 'capable', lambda x: False)
             if capable('subversion'):

--- a/hgsubversion/util.py
+++ b/hgsubversion/util.py
@@ -150,27 +150,13 @@ def pickle_atomic(data, file_path):
     """
     f = hgutil.atomictempfile(file_path, 'w+b', 0644)
     pickle.dump(data, f)
-    # Older versions of hg have .rename() instead of .close on
-    # atomictempfile.
-    if getattr(hgutil.atomictempfile, 'rename', False):
-        f.rename()
-    else:
-        f.close()
+    f.close()
 
 def parseurl(url, heads=[]):
-    parsed = hg.parseurl(url, heads)
-    if len(parsed) == 3:
-        # old hg, remove when we can be 1.5-only
-        svn_url, heads, checkout = parsed
-    else:
-        svn_url, heads = parsed
-        if isinstance(heads, tuple) and len(heads) == 2:
-            # hg 1.6 or later
-            _junk, heads = heads
-        if heads:
-            checkout = heads[0]
-        else:
-            checkout = None
+    checkout = None
+    svn_url, (_junk, heads) = hg.parseurl(url, heads)
+    if heads:
+        checkout = heads[0]
     return svn_url, heads, checkout
 
 

--- a/hgsubversion/wrappers.py
+++ b/hgsubversion/wrappers.py
@@ -563,11 +563,7 @@ def clone(orig, ui, source, dest=None, *
 
     data = {}
     def hgclonewrapper(orig, ui, *args, **opts):
-        if getattr(hg, 'peer', None):
-            # Since 1.9 (d976542986d2)
-            origsource = args[1]
-        else:
-            origsource = args[0]
+        origsource = args[1]
 
         if isinstance(origsource, str):
             source, branch, checkout = util.parseurl(ui.expandpath(origsource),
@@ -602,14 +598,11 @@ def clone(orig, ui, source, dest=None, *
 
     dstrepo = data.get('dstrepo')
     srcrepo = data.get('srcrepo')
+    dst = dstrepo.local()
 
     if dstrepo.local() and srcrepo.capable('subversion'):
         dst = dstrepo.local()
-        if isinstance(dst, bool):
-            # Apparently <= hg@1.9
-            fd = dstrepo.opener("hgrc", "a", text=True)
-        else:
-            fd = dst.opener("hgrc", "a", text=True)
+        fd = dst.opener("hgrc", "a", text=True)
         preservesections = set(s for s, v in optionmap.itervalues())
         preservesections |= extrasections
         for section in preservesections: