hgweb: detect change based on changelog size too

Before, there was a race between an access and a modification made
within the same second.

mercurial/hgweb/common.py

@@ -86,12 +86,16 b' def _statusmessage(code):'
 def statusmessage(code, message=None):
     return '%d %s' % (code, message or _statusmessage(code))
 
-def get_mtime(spath):
+def get_stat(spath):
+    """stat changelog if it exists, spath otherwise"""
     cl_path = os.path.join(spath, "00changelog.i")
     if os.path.exists(cl_path):
-        return os.stat(cl_path).st_mtime
+        return os.stat(cl_path)
     else:
-        return os.stat(spath).st_mtime
+        return os.stat(spath)
+
+def get_mtime(spath):
+    return get_stat(spath).st_mtime
 
 def staticfile(directory, fname, req):
     """return a file inside directory with guessed Content-Type header

mercurial/hgweb/hgweb_mod.py

@@ -8,7 +8,7 b''
 
 import os
 from mercurial import ui, hg, hook, error, encoding, templater
-from common import get_mtime, ErrorResponse, permhooks, caching
+from common import get_stat, ErrorResponse, permhooks, caching
 from common import HTTP_OK, HTTP_NOT_MODIFIED, HTTP_BAD_REQUEST
 from common import HTTP_NOT_FOUND, HTTP_SERVER_ERROR
 from request import wsgirequest
@@ -38,6 +38,7 b' class hgweb(object):'
         self.repo.ui.setconfig('ui', 'interactive', 'off')
         hook.redirect(True)
         self.mtime = -1
+        self.size = -1
         self.reponame = name
         self.archives = 'zip', 'gz', 'bz2'
         self.stripecount = 1
@@ -62,9 +63,12 b' class hgweb(object):'
     def refresh(self, request=None):
         if request:
             self.repo.ui.environ = request.env
-        mtime = get_mtime(self.repo.spath)
-        if mtime != self.mtime:
-            self.mtime = mtime
+        st = get_stat(self.repo.spath)
+        # compare changelog size in addition to mtime to catch
+        # rollbacks made less than a second ago
+        if st.st_mtime != self.mtime or st.st_size != self.size:
+            self.mtime = st.st_mtime
+            self.size = st.st_size
             self.repo = hg.repository(self.repo.ui, self.repo.root)
             self.maxchanges = int(self.config("web", "maxchanges", 10))
             self.stripecount = int(self.config("web", "stripes", 1))

tests/test-rollback.t

@@ -92,3 +92,29 b' same thing, but run $EDITOR'
   $ cat .hg/last-message.txt
   another precious commit message
 
+test rollback on served repository
+
+  $ hg commit -m "precious commit message"
+  $ hg serve -p $HGPORT -d --pid-file=hg.pid -A access.log -E errors.log
+  $ cat hg.pid >> $DAEMON_PIDS
+  $ cd ..
+  $ hg clone http://localhost:$HGPORT u
+  requesting all changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files
+  updating to branch test
+  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
+  $ cd u
+  $ hg id default
+  1df294f7b1a2
+
+now rollback and observe that 'hg serve' reloads the repository and
+presents the correct tip changeset:
+
+  $ hg -R ../t rollback
+  repository tip rolled back to revision -1 (undo commit)
+  working directory now based on revision -1
+  $ hg id default
+  000000000000