profile: expand PID in output file name

doc/hgrc.5.txt

@@ -412,7 +412,10 b' profile::'
     "hotshot" is deprecated, and produces less reliable results.
     Default is no profiling.
   output;;
-    The name of a file to write profiling data to.  Default is stderr.
+    The name of a file to write profiling data to.  Each occurrence of
+    "%%p" will be replaced with the current process ID (the repeated
+    "%" protects against the config parser's string interpolator).
+    Default output is to stderr.
   
 server::
   Controls generic server settings.

mercurial/dispatch.py

@@ -379,7 +379,8 b' def profiled(ui, func, options={}):'
     def profile_fp():
         outfile = ui.config('profile', 'output', untrusted=True)
         if outfile:
-            return open(outfile, 'w')
+            pid = str(os.getpid())
+            return open(outfile.replace('%p', pid), 'w')
         else:
             return sys.stderr