Extend the git-cl-comments command functionality
Extend the git-cl-comments command functionality

The "comments" command is taught to:
- accept an arbitrary review issue id;
- post comments on the current or specified review issue.

This is required for the auto-rebaseline bot to notify a
rebaseline requestor of the fact that the rebaseline has happened
by means of posting a comment to the review issue that requested
the rebaseline, as suggested by iannucci@.

R=iannucci, szager, dpranke

Review URL: https://codereview.chromium.org/693873002

git-svn-id: fd409f4bdeea2bb50a5d34bb4d4bfc2046a5a3dd@292844 0039d316-1c4b-4281-b951-d872f2087c98

michalliu/chromium-depot_tools,duanwujie/depot_tools,CoherentLabs/depot_tools,disigma/depot_tools,withtone/depot_tools,aleonliao/depot_tools,npe9/depot_tools,disigma/depot_tools,mlufei/depot_tools,withtone/depot_tools,Midrya/chromium,Midrya/chromium,HackFisher/depot_tools,fracting/depot_tools,HackFisher/depot_tools,sarvex/depot-tools,aleonliao/depot_tools,chinmaygarde/depot_tools,G-P-S/depot_tools,eatbyte/depot_tools,G-P-S/depot_tools,liaorubei/depot_tools,kaiix/depot_tools,xuyuhan/depot_tools,kaiix/depot_tools,aleonliao/depot_tools,azureplus/chromium_depot_tools,fanjunwei/depot_tools,CoherentLabs/depot_tools,G-P-S/depot_tools,npe9/depot_tools,ajohnson23/depot_tools,gcodetogit/depot_tools,airtimemedia/depot_tools,chinmaygarde/depot_tools,azunite/chrome_build,HackFisher/depot_tools,primiano/depot_tools,SuYiling/chrome_depot_tools,chinmaygarde/depot_tools,disigma/depot_tools,fracting/depot_tools,duanwujie/depot_tools,liaorubei/depot_tools,azureplus/chromium_depot_tools,npe9/depot_tools,eatbyte/depot_tools,michalliu/chromium-depot_tools,gcodetogit/depot_tools,mlufei/depot_tools,SuYiling/chrome_depot_tools,duongbaoduy/gtools,duanwujie/depot_tools,ajohnson23/depot_tools,Midrya/chromium,G-P-S/depot_tools,xuyuhan/depot_tools,duongbaoduy/gtools,ajohnson23/depot_tools,duongbaoduy/gtools,gcodetogit/depot_tools,fanjunwei/depot_tools,hsharsha/depot_tools,azunite/chrome_build,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,michalliu/chromium-depot_tools,eatbyte/depot_tools,primiano/depot_tools,xuyuhan/depot_tools,hsharsha/depot_tools,npe9/depot_tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,eatbyte/depot_tools,azureplus/chromium_depot_tools,xuyuhan/depot_tools,primiano/depot_tools,airtimemedia/depot_tools,airtimemedia/depot_tools,sarvex/depot-tools,sarvex/depot-tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,michalliu/chromium-depot_tools,HackFisher/depot_tools,airtimemedia/depot_tools,liaorubei/depot_tools,SuYiling/chrome_depot_tools,liaorubei/depot_tools,azunite/chrome_build,sarvex/depot-tools,mlufei/depot_tools,withtone/depot_tools,kaiix/depot_tools,hsharsha/depot_tools,fracting/depot_tools,fanjunwei/depot_tools,fanjunwei/depot_tools