Update .git/objects/info/alternates when upstream url changes.
Update .git/objects/info/alternates when upstream url changes.

BUG=497943
R=hinoka@chromium.org,agable@chromium.org

Review URL: https://codereview.chromium.org/1163403003

git-svn-id: fd409f4bdeea2bb50a5d34bb4d4bfc2046a5a3dd@295568 0039d316-1c4b-4281-b951-d872f2087c98

CoherentLabs/depot_tools,duongbaoduy/gtools,gcodetogit/depot_tools,disigma/depot_tools,duongbaoduy/gtools,chinmaygarde/depot_tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,mlufei/depot_tools,kaiix/depot_tools,fracting/depot_tools,gcodetogit/depot_tools,ajohnson23/depot_tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,Midrya/chromium,aleonliao/depot_tools,kaiix/depot_tools,azureplus/chromium_depot_tools,azunite/chrome_build,aleonliao/depot_tools,SuYiling/chrome_depot_tools,disigma/depot_tools,chinmaygarde/depot_tools,SuYiling/chrome_depot_tools,disigma/depot_tools,hsharsha/depot_tools,primiano/depot_tools,azureplus/chromium_depot_tools,primiano/depot_tools,Midrya/chromium,mlufei/depot_tools,fracting/depot_tools,hsharsha/depot_tools,CoherentLabs/depot_tools,kaiix/depot_tools,Midrya/chromium,duongbaoduy/gtools,azureplus/chromium_depot_tools,duanwujie/depot_tools,azunite/chrome_build,ajohnson23/depot_tools,duanwujie/depot_tools,primiano/depot_tools,cpanelli/-git-clone-https-chromium.googlesource.com-chromium-tools-depot_tools,mlufei/depot_tools,SuYiling/chrome_depot_tools,aleonliao/depot_tools,hsharsha/depot_tools,gcodetogit/depot_tools,fracting/depot_tools,ajohnson23/depot_tools,chinmaygarde/depot_tools,duanwujie/depot_tools,azunite/chrome_build