hg: recognize include and exclude patterns when cloning

This commit teaches clone() to accept arguments defining file
patterns to clone. This is the first step in teaching core code
about the existence of a narrow clone.

Right now, we only perform validation of the arguments and pass
additional options into createopts to influence repository
creation. Nothing of consequence happens with that creation option
yet, however.

For now, arbitrary restrictions exist, such as not allowing patterns
for shared repos and disabling local copies when patterns are
defined. We can potentially lift these restrictions in the future
once partial clone/storage support is more flushed out. I figure
it is best to reduce the surface area for bugs for the time being.

It may seem weird to prefix these arguments with "store." However,
clone is effectively pull + update and file patterns could apply to
both the store and the working directory. The prefix is there to
disambiguate in the future when this function may want to use
different sets of patterns for the store and working directory.

Differential Revision: https://phab.mercurial-scm.org/D4536

mercurial/hg.py

@@ -35,6 +35,7 b' from . import ('
     logcmdutil,
     logexchange,
     merge as mergemod,
+    narrowspec,
     node,
     phases,
     scmutil,
@@ -500,7 +501,8 b' def _copycache(srcrepo, dstcachedir, fna'
         util.copyfile(srcbranchcache, dstbranchcache)
 
 def clone(ui, peeropts, source, dest=None, pull=False, revs=None,
-          update=True, stream=False, branch=None, shareopts=None):
+          update=True, stream=False, branch=None, shareopts=None,
+          storeincludepats=None, storeexcludepats=None):
     """Make a copy of an existing repository.
 
     Create a copy of an existing repository in a new directory.  The
@@ -542,6 +544,13 b' def clone(ui, peeropts, source, dest=Non'
     repository. "identity" means the name is derived from the node of the first
     changeset in the repository. "remote" means the name is derived from the
     remote's path/URL. Defaults to "identity."
+
+    storeincludepats and storeexcludepats: sets of file patterns to include and
+    exclude in the repository copy, respectively. If not defined, all files
+    will be included (a "full" clone). Otherwise a "narrow" clone containing
+    only the requested files will be performed. If ``storeincludepats`` is not
+    defined but ``storeexcludepats`` is, ``storeincludepats`` is assumed to be
+    ``path:.``. If both are empty sets, no files will be cloned.
     """
 
     if isinstance(source, bytes):
@@ -574,6 +583,24 b' def clone(ui, peeropts, source, dest=Non'
         elif destvfs.listdir():
             raise error.Abort(_("destination '%s' is not empty") % dest)
 
+    createopts = {}
+    narrow = False
+
+    if storeincludepats is not None:
+        narrowspec.validatepatterns(storeincludepats)
+        narrow = True
+
+    if storeexcludepats is not None:
+        narrowspec.validatepatterns(storeexcludepats)
+        narrow = True
+
+    if narrow:
+        # Include everything by default if only exclusion patterns defined.
+        if storeexcludepats and not storeincludepats:
+            storeincludepats = {'path:.'}
+
+        createopts['narrowfiles'] = True
+
     shareopts = shareopts or {}
     sharepool = shareopts.get('pool')
     sharenamemode = shareopts.get('mode')
@@ -605,6 +632,11 b' def clone(ui, peeropts, source, dest=Non'
             raise error.Abort(_('unknown share naming mode: %s') %
                               sharenamemode)
 
+        # TODO this is a somewhat arbitrary restriction.
+        if narrow:
+            ui.status(_('(pooled storage not supported for narrow clones)\n'))
+            sharepath = None
+
         if sharepath:
             return clonewithshare(ui, peeropts, sharepath, source, srcpeer,
                                   dest, pull=pull, rev=revs, update=update,
@@ -625,6 +657,10 b' def clone(ui, peeropts, source, dest=Non'
             and not phases.hassecret(srcrepo)):
             copy = not pull and not revs
 
+        # TODO this is a somewhat arbitrary restriction.
+        if narrow:
+            copy = False
+
         if copy:
             try:
                 # we use a lock here because if we race with commit, we
@@ -671,8 +707,9 b' def clone(ui, peeropts, source, dest=Non'
                           node=node.hex(node.nullid))
         else:
             try:
-                destpeer = peer(srcrepo or ui, peeropts, dest, create=True)
-                                # only pass ui when no srcrepo
+                # only pass ui when no srcrepo
+                destpeer = peer(srcrepo or ui, peeropts, dest, create=True,
+                                createopts=createopts)
             except OSError as inst:
                 if inst.errno == errno.EEXIST:
                     cleandir = None
@@ -714,6 +751,12 b' def clone(ui, peeropts, source, dest=Non'
                     exchange.pull(local, srcpeer, revs,
                                   streamclonerequested=stream)
             elif srcrepo:
+                # TODO lift restriction once exchange.push() accepts narrow
+                # push.
+                if narrow:
+                    raise error.Abort(_('narrow clone not available for '
+                                        'remote destinations'))
+
                 exchange.push(srcrepo, destpeer, revs=revs,
                               bookmarks=srcrepo._bookmarks.keys())
             else: