[PATCH 3 of 4] lock message: write lock description to a file

[Tuli Uchitel]

# HG changeset patch
# User Tuli Uchitel <tuli at fb.com>
# Date 1457463953 0
#      Tue Mar 08 19:05:53 2016 +0000
# Branch stable
# Node ID d3da9ce4c07018109275c91e41b2c33231449104
# Parent  1ffef024963c56879289caf534575d0c72f4b7e9
lock message: write lock description to a file

implement a method that writes a message to a special file associated with the lock and use it for auditing the case when the user opens an editor session when required

diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
--- a/mercurial/cmdutil.py
+++ b/mercurial/cmdutil.py
@@ -2717,6 +2717,13 @@
     repo.dirstate.write(tr)
     pending = tr and tr.writepending() and repo.root
 
+    # Trace user requested to open an editor session
+    currentwlock = repo.currentwlock()
+    if isinstance(currentwlock, lockmod.lock):
+        locklogmessage = _("user {} requested to open a {} session on host {}").format(
+            ctx.user(), repo.ui.geteditor(), currentwlock.host)
+        currentwlock.writelocklogmessage(locklogmessage)
+
     editortext = repo.ui.edit(committext, ctx.user(), ctx.extra(),
                         editform=editform, pending=pending)
     text = re.sub("(?m)^HG:.*(\n|$)", "", editortext)
diff --git a/mercurial/lock.py b/mercurial/lock.py
--- a/mercurial/lock.py
+++ b/mercurial/lock.py
@@ -47,6 +47,7 @@
                  desc=None, inheritchecker=None, parentlock=None):
         self.vfs = vfs
         self.f = file
+        self.lockdescriptionfilename = "%s.description" % self.f
         self.held = 0
         self.timeout = timeout
         self.releasefn = releasefn
@@ -78,6 +79,10 @@
         # wrapper around os.getpid() to make testing easier
         return os.getpid()
 
+    def writelocklogmessage(self, lockdescriptionmessage):
+        fp = self.vfs(self.lockdescriptionfilename, mode='wb')
+        fp.write(lockdescriptionmessage)
+
     def lock(self):
         timeout = self.timeout
         while True:
@@ -226,6 +231,7 @@
                 if not self._parentheld:
                     try:
                         self.vfs.unlink(self.f)
+                        self.vfs.unlink(self.lockdescriptionfilename)
                     except OSError:
                         pass
             # The postrelease functions typically assume the lock is not held