Add timestamps to log. Log channel traffic.

.gitignore

@@ -1,5 +1,5 @@
 /doc/tags
 /misc
 /test/*.actual
-gitgutter.log
+*.log
 

autoload/gitgutter/debug.vim

@@ -1,4 +1,8 @@
-let s:log_file = expand('<sfile>:p:h:h:h').'/'.'gitgutter.log'
+let s:plugin_dir  = expand('<sfile>:p:h:h:h').'/'
+let s:log_file    = s:plugin_dir.'gitgutter.log'
+let s:channel_log = s:plugin_dir.'channel.log'
+let s:new_log_session = 1
+
 
 function! gitgutter#debug#debug()
   " Open a scratch buffer
@@ -75,16 +79,39 @@ endfunction
 " assumes optional args are calling function's optional args
 function! gitgutter#debug#log(message, ...)
   if g:gitgutter_log
+    if s:new_log_session && gitgutter#async#available()
+      call ch_logfile(s:channel_log, 'w')
+    endif
+
     execute 'redir >> '.s:log_file
+      if s:new_log_session
+        let s:start = reltime()
+        silent echo "\n==== start log session ===="
+      endif
+
+      let elapsed = reltimestr(reltime(s:start)).' '
+      silent echo ''
       " callers excluding this function
-      silent echo "\n".expand('<sfile>')[:-22].':'
-      silent echo type(a:message) == 1 ? join(split(a:message, '\n'),"\n") : a:message
+      silent echo elapsed.expand('<sfile>')[:-22].':'
+      silent echo elapsed.s:format_for_log(a:message)
       if a:0 && !empty(a:1)
         for msg in a:000
-          silent echo type(msg) == 1 ? join(split(msg, '\n'),"\n") : msg
+          silent echo elapsed.s:format_for_log(msg)
         endfor
       endif
     redir END
+
+    let s:new_log_session = 0
+  endif
+endfunction
+
+function! s:format_for_log(data)
+  if type(a:data) == 1
+    return join(split(a:data,'\n'),"\n")
+  elseif type(a:data) == 3
+    return '['.join(a:data,"\n").']'
+  else
+    return a:data
   endif
 endfunction