dirstate: add identity information to detect simultaneous changing in storage
authorFUJIWARA Katsunori <foozy@lares.dti.ne.jp>
Fri, 09 Jun 2017 13:07:48 +0900
changeset 32750 b698921ee137
parent 32749 b5524fd9a4e3
child 32751 627eaab1ad07
dirstate: add identity information to detect simultaneous changing in storage This identity is used to examine whether dirstate is simultaneously changed in storage after previous caching (see issue5584 for detail). util.cachestat can't be used for this purpose, because it has no valuable information on Windows. On the other hand, util.filestat can detect changing dirstate in storage certainly, regardless of platforms. https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan Strictly speaking, if underlying filesystem doesn't support ctime/mtime, util.filestat can't detect simultaneous changing in storage as expected. But simultaneous changing on such (very rare) platform can't be detected regardless of this patch series. Therefore, util.filestat should be reasonable identity for almost all usecases.
mercurial/dirstate.py
--- a/mercurial/dirstate.py	Fri Jun 09 13:07:48 2017 +0900
+++ b/mercurial/dirstate.py	Fri Jun 09 13:07:48 2017 +0900
@@ -159,6 +159,11 @@
         return self._copymap
 
     @propertycache
+    def _identity(self):
+        self._read()
+        return self._identity
+
+    @propertycache
     def _nonnormalset(self):
         nonnorm, otherparents = nonnormalentries(self._map)
         self._otherparentset = otherparents
@@ -426,6 +431,8 @@
     def _read(self):
         self._map = {}
         self._copymap = {}
+        # ignore HG_PENDING because identity is used only for writing
+        self._identity = util.filestat(self._opener.join(self._filename))
         try:
             fp = self._opendirstatefile()
             try:
@@ -476,7 +483,8 @@
         rereads the dirstate. Use localrepo.invalidatedirstate() if you want to
         check whether the dirstate has changed before rereading it.'''
 
-        for a in ("_map", "_copymap", "_filefoldmap", "_dirfoldmap", "_branch",
+        for a in ("_map", "_copymap", "_identity",
+                  "_filefoldmap", "_dirfoldmap", "_branch",
                   "_pl", "_dirs", "_ignore", "_nonnormalset",
                   "_otherparentset"):
             if a in self.__dict__:
@@ -741,6 +749,14 @@
 
         self._dirty = True
 
+    def identity(self):
+        '''Return identity of dirstate itself to detect changing in storage
+
+        If identity of previous dirstate is equal to this, writing
+        changes based on the former dirstate out can keep consistency.
+        '''
+        return self._identity
+
     def write(self, tr):
         if not self._dirty:
             return