Refactoring: Extract interface for VC in release scripts.

Also simplify tagging in merge_to_branch.

BUG=chromium:410721
LOG=n
R=jkummerow@chromium.org, tandrii@chromium.org

Review URL: https://codereview.chromium.org/607463002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24228 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Ignore generated JSON files for TurboFan graphs.

R=danno@chromium.org

Review URL: https://codereview.chromium.org/605733002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24229 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Disable version increment and tagging until after the git migration.

BUG=chromium:410721
LOG=n
TBR=tandrii@chromium.org

Review URL: https://codereview.chromium.org/609443002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@24230 ce2b1a6d-e550-0410-aec6-3dcde31c8c00
Merge remote-tracking branch 'upstream/master'