Automatic nesting into running transactions in the same repository.

Automatic nesting into running transactions in the same repository.

This associates a transaction handle with a given repository object, and
any additional calls to start new transactions reuse that transaction.

For the 2700 patch import run, this brings the system time down from
1m20s to 50s, mostly by skipping backups of the dirstate file.

(note, this patch does not change hg import to use the nested transaction,
mq is the only user right now)

--- a/mercurial/localrepo.py	Tue Feb 28 11:49:35 2006 -0600
+++ b/mercurial/localrepo.py	Tue Feb 28 12:24:54 2006 -0600
@@ -13,6 +13,8 @@
 demandload(globals(), "re lock transaction tempfile stat mdiff errno")
 
 class localrepository(object):
+    def __del__(self):
+        self.transhandle = None
     def __init__(self, ui, path=None, create=0):
         if not path:
             p = os.getcwd()
@@ -37,6 +39,7 @@
         self.nodetagscache = None
         self.encodepats = None
         self.decodepats = None
+        self.transhandle = None
 
         if create:
             os.mkdir(self.path)
@@ -215,6 +218,10 @@
         return self.wopener(filename, 'w').write(data)
 
     def transaction(self):
+        tr = self.transhandle
+        if tr != None and tr.running():
+            return tr.nest()
+
         # save dirstate for undo
         try:
             ds = self.opener("dirstate").read()
@@ -222,13 +229,11 @@
             ds = ""
         self.opener("journal.dirstate", "w").write(ds)
 
-        def after():
-            util.rename(self.join("journal"), self.join("undo"))
-            util.rename(self.join("journal.dirstate"),
-                        self.join("undo.dirstate"))
-
-        return transaction.transaction(self.ui.warn, self.opener,
-                                       self.join("journal"), after)
+        tr = transaction.transaction(self.ui.warn, self.opener,
+                                       self.join("journal"), 
+                                       aftertrans(self.path))
+        self.transhandle = tr
+        return tr
 
     def recover(self):
         l = self.lock()
@@ -1879,3 +1884,13 @@
         if errors[0]:
             self.ui.warn(_("%d integrity errors encountered!\n") % errors[0])
             return 1
+
+# used to avoid circular references so destructors work
+def aftertrans(base):
+    p = base
+    def a():
+        util.rename(os.path.join(p, "journal"), os.path.join(p, "undo"))
+        util.rename(os.path.join(p, "journal.dirstate"),
+                    os.path.join(p, "undo.dirstate"))
+    return a
+

--- a/mercurial/transaction.py	Tue Feb 28 11:49:35 2006 -0600
+++ b/mercurial/transaction.py	Tue Feb 28 12:24:54 2006 -0600
@@ -22,6 +22,7 @@
         if os.path.exists(journal):
             raise AssertionError(_("journal already exists - run hg recover"))
 
+        self.count = 1
         self.report = report
         self.opener = opener
         self.after = after
@@ -46,7 +47,17 @@
         self.file.write("%s\0%d\n" % (file, offset))
         self.file.flush()
 
+    def nest(self):
+        self.count += 1
+        return self
+
+    def running(self):
+        return self.count > 0
+
     def close(self):
+        self.count -= 1
+        if self.count != 0:
+            return
         self.file.close()
         self.entries = []
         if self.after: