[#403] Update cobra-generated doc with "retro" subcommand

Author: mengdaming

doc/tcr.md

@@ -41,6 +41,7 @@ tcr [flags]
 * [tcr log](tcr_log.md)	 - Print the TCR commit history
 * [tcr mob](tcr_mob.md)	 - Run TCR in mob mode
 * [tcr one-shot](tcr_one-shot.md)	 - Run one TCR cycle and exit
+* [tcr retro](tcr_retro.md)	 - Generate retrospective template with stats
 * [tcr solo](tcr_solo.md)	 - Run TCR in solo mode
 * [tcr stats](tcr_stats.md)	 - Print TCR stats
 * [tcr web](tcr_web.md)	 - Run TCR with web user interface (experimental)

doc/tcr_retro.md

@@ -0,0 +1,53 @@
+## tcr retro
+
+Generate retrospective template with stats
+
+### Synopsis
+
+
+TCR retro subcommand generates a retrospective template in markdown format prefilled with TCR execution info.
+The markdown file is saved into the TCR base directory with the name 'tcr-retro.md'. 
+
+The following information is included in the markdown:
+
+- Average size of changes per passing commit 
+- Average size of changes per failing commit
+
+These stats are extracted for the repository containing TCR base directory (cf. -b option). 
+The branch is the current working branch set for this repository.
+
+This subcommand does not start TCR engine.
+
+```
+tcr retro [flags]
+```
+
+### Options
+
+```
+  -h, --help   help for retro
+```
+
+### Options inherited from parent commands
+
+```
+  -p, --auto-push               enable VCS push after every commit
+  -b, --base-dir string         indicate the directory from which TCR is looking for files (default: current directory)
+  -c, --config-dir string       indicate the directory where TCR configuration is stored (default: current directory)
+  -d, --duration duration       set the duration for role rotation countdown timer
+  -g, --git-remote string       name of the git remote repository to sync with (default: "origin")
+  -l, --language string         indicate the programming language to be used by TCR
+  -m, --message-suffix string   indicate text to append at the end of TCR commit messages (ex: "[#1234]")
+  -o, --polling duration        set VCS polling period when running as navigator
+  -P, --port-number int         indicate port number used by TCR HTTP server in web mode (experimental) (default: 8483)
+  -t, --toolchain string        indicate the toolchain to be used by TCR
+  -T, --trace string            indicate trace options. Recognized values: none (default), vcs or http
+  -r, --variant string          indicate the variant to be used by TCR: relaxed (default), btcr, or introspective
+  -V, --vcs string              indicate the VCS (version control system) to be used by TCR: git (default) or p4
+  -w, --work-dir string         indicate the directory from which TCR is running (default: current directory)
+```
+
+### SEE ALSO
+
+* [tcr](tcr.md)	 - TCR (Test && Commit || Revert)
+