add "requires" file to the repo, specifying the requirements

tests/test-requires

@@ -0,0 +1,14 b''
+#!/bin/sh
+
+mkdir t
+cd t
+hg init
+echo a > a
+hg add a
+hg commit -m test -d "1000000 0"
+rm .hg/requires
+hg tip
+echo indoor-pool > .hg/requires
+hg tip
+
+true

tests/test-requires.out

@@ -0,0 +1,7 b''
+changeset:   0:0acdaf898367
+tag:         tip
+user:        test
+date:        Mon Jan 12 13:46:40 1970 +0000
+summary:     test
+
+abort: requirement 'indoor-pool' not supported!

mercurial/hg.py

@@ -149,13 +149,23 b' def clone(ui, source, dest=None, pull=Fa'
             copy = False
 
     if copy:
-        # we lock here to avoid premature writing to the target
+        def force_copy(src, dst):
+            try:
+                util.copyfiles(src, dst)
+            except OSError, inst:
+                if inst.errno != errno.ENOENT:
+                    raise
+
         src_store = os.path.realpath(src_repo.spath)
         dest_path = os.path.realpath(os.path.join(dest, ".hg"))
         dest_store = dest_path
         if not os.path.exists(dest):
             os.mkdir(dest)
         os.mkdir(dest_path)
+        # copy the requires file
+        force_copy(src_repo.join("requires"),
+                   os.path.join(dest_path, "requires"))
+        # we lock here to avoid premature writing to the target
         dest_lock = lock.lock(os.path.join(dest_store, "lock"))
 
         files = ("data",
@@ -164,11 +174,7 b' def clone(ui, source, dest=None, pull=Fa'
         for f in files:
             src = os.path.join(src_store, f)
             dst = os.path.join(dest_store, f)
-            try:
-                util.copyfiles(src, dst)
-            except OSError, inst:
-                if inst.errno != errno.ENOENT:
-                    raise
+            force_copy(src, dst)
 
         # we need to re-init the repo after manually copying the data
         # into it

mercurial/localrepo.py

@@ -16,6 +16,7 b' demandload(globals(), "os revlog time ut'
 
 class localrepository(repo.repository):
     capabilities = ('lookup', 'changegroupsubset')
+    supported = ('revlogv1',)
 
     def __del__(self):
         self.transhandle = None
@@ -44,10 +45,27 b' class localrepository(repo.repository):'
                 os.mkdir(self.path)
                 #if self.spath != self.path:
                 #    os.mkdir(self.spath)
+                requirements = ("revlogv1",)
+                reqfile = self.opener("requires", "w")
+                for r in requirements:
+                    reqfile.write("%s\n" % r)
+                reqfile.close()
             else:
                 raise repo.RepoError(_("repository %s not found") % path)
         elif create:
             raise repo.RepoError(_("repository %s already exists") % path)
+        else:
+            # find requirements
+            try:
+                requirements = self.opener("requires").read().splitlines()
+            except IOError, inst:
+                if inst.errno != errno.ENOENT:
+                    raise
+                requirements = []
+        # check them
+        for r in requirements:
+            if r not in self.supported:
+                raise repo.RepoError(_("requirement '%s' not supported") % r)
 
         # setup store
         self.spath = self.path

mercurial/statichttprepo.py

@@ -37,7 +37,20 b' class statichttprepository(localrepo.loc'
         self.ui = ui
         self.revlogversion = 0
         self.opener = opener(self.path)
+        # find requirements
+        try:
+            requirements = self.opener("requires").read().splitlines()
+        except IOError:
+            requirements = []
+        # check them
+        for r in requirements:
+            if r not in self.supported:
+                raise repo.RepoError(_("requirement '%s' not supported") % r)
+
+        # setup store
+        self.spath = self.path
         self.sopener = opener(self.spath)
+
         self.manifest = manifest.manifest(self.sopener)
         self.changelog = changelog.changelog(self.sopener)
         self.tagscache = None

tests/test-hup.out

@@ -6,3 +6,4 b' transaction abort!'
 rollback completed
 00changelog.i
 journal.dirstate
+requires