2.2.0

CHANGES:

• Fix the github markdown syntax generated by opam-publish [#131 @liyishuai]
• Disambiguate GitHub archive URL computed from repository and tag [#135 @ilankri]
• Upgrade to cmdliner >= 1.1.0 [#134 @ilankri]
• Support git remotes with multiple push targets [#137 @favonia]
• Fix broken state if the initial opam-repository clone fails [#140 @kit-ty-kate - fix #86]
• Shorten the generated branch name [#141 @kit-ty-kate - fix #139]