blackbox: add configitem for format of log timestamps

Sometimes blackbox logs are used to report performance problems, but the
timestamps are only at second granularity, so often the timings have to
stated separately by the reporter. This is inconvenient and error-prone,
so I would like to include %f in the date format. This patch makes that
possible.

hgext/blackbox.py

@@ -33,6 +33,11 b' Examples::'
   # rotate up to N log files when the current one gets too big
   maxfiles = 3
 
+  [blackbox]
+  # Include nanoseconds in log entries with %f (see Python function
+  # datetime.datetime.strftime)
+  date-format = '%Y-%m-%d @ %H:%M:%S.%f'
+
 """
 
 from __future__ import absolute_import
@@ -82,6 +87,9 b" configitem('blackbox', 'maxfiles',"
 configitem('blackbox', 'track',
     default=lambda: ['*'],
 )
+configitem('blackbox', 'date-format',
+    default='%Y/%m/%d %H:%M:%S',
+)
 
 lastui = None
 
@@ -169,7 +177,8 b' def wrapui(ui):'
                 return
             ui._bbinlog = True
             default = self.configdate('devel', 'default-date')
-            date = dateutil.datestr(default, '%Y/%m/%d %H:%M:%S')
+            date = dateutil.datestr(default,
+                                    ui.config('blackbox', 'date-format'))
             user = procutil.getuser()
             pid = '%d' % procutil.getpid()
             formattedmsg = msg[0] % msg[1:]

tests/test-blackbox.t

@@ -82,6 +82,16 b' recursive aliases work correctly'
   1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> so-confusing exited 0 after * seconds (glob)
   1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> blackbox
 
+custom date format
+  $ rm ./.hg/blackbox.log
+  $ hg --config blackbox.date-format='%Y-%m-%d @ %H:%M:%S' \
+  >    --config devel.default-date='1334347993 0' --traceback status
+  A a
+  $ hg blackbox
+  2012-04-13 @ 20:13:13 bob @0000000000000000000000000000000000000000 (5000)> --config 'blackbox.date-format=%Y-%m-%d @ %H:%M:%S' --config 'devel.default-date=1334347993 0' --traceback status
+  2012-04-13 @ 20:13:13 bob @0000000000000000000000000000000000000000 (5000)> --config 'blackbox.date-format=%Y-%m-%d @ %H:%M:%S' --config 'devel.default-date=1334347993 0' --traceback status exited 0 after * seconds (glob)
+  1970/01/01 00:00:00 bob @0000000000000000000000000000000000000000 (5000)> blackbox
+
 incoming change tracking
 
 create two heads to verify that we only see one change in the log later