profiling: Adding profiling.output config variable

If specified, outputs profiling data to the said file.
Prints to stderr by default

doc/hgrc.5.txt

@@ -538,6 +538,18 b' paths::'
     Optional. Directory or URL to use when pushing if no destination
     is specified.
 
+[[profiling]]
+profiling::
+  Specifies profiling format and file output.
+  In this section description, 'profiling data' stands for the raw data
+  collected during profiling, while 'profiling report' stands for a
+  statistical text report generated from the profiling data.
+  The profiling is done using lsprof.
+  output;;
+    File path where profiling data or report should be saved.
+    If the file exists, it is replaced.
+    Default: None, data is printed on stderr
+
 [[server]]
 server::
   Controls generic server settings.

mercurial/dispatch.py

@@ -379,6 +379,15 b' def _runcommand(ui, options, cmd, cmdfun'
             raise error.ParseError(cmd, _("invalid arguments"))
 
     if options['profile']:
+        output = ui.config('profiling', 'output')
+
+        if output:
+            path = os.path.expanduser(output)
+            path = ui.expandpath(path)
+            ostream = open(path, 'wb')
+        else:
+            ostream = sys.stderr
+
         try:
             from mercurial import lsprof
         except ImportError:
@@ -393,6 +402,9 b' def _runcommand(ui, options, cmd, cmdfun'
             p.disable()
             stats = lsprof.Stats(p.getstats())
             stats.sort()
-            stats.pprint(top=10, file=sys.stderr, climit=5)
+            stats.pprint(top=10, file=ostream, climit=5)
+
+            if output:
+                ostream.close()
     else:
         return checkargs()

tests/test-profile

@@ -3,7 +3,16 b''
 echo % test --time
 hg --time help -q help 2>&1 | grep Time > /dev/null || echo --time failed
 
+hg init a
+cd a
+
 echo % test --profile
 if "$TESTDIR/hghave" -q lsprof; then
-    hg --profile help -q help 2>&1 | grep CallCount > /dev/null || echo --profile failed
+    hg --profile st 2>../out || echo --profile failed
+    grep CallCount < ../out > /dev/null || echo wrong --profile
+
+    hg --profile --config profiling.output=../out st 2>&1 \
+        || echo --profile + output to file failed
+    grep CallCount < ../out > /dev/null \
+        || echo wrong --profile output when saving to a file
 fi