git branches can share local clones

Dependencies

• [2] UO67NQMR Change `fetchInputGit' to do `git clone -b BRANCH' instead of `git clone'.
• [3] SHYRGAWZ hydra: when no external url is given for diff's of git/hg input, revert to a diff done on a local available clone
• [4] C7CXMZ66 hydra: do not perform git clone every time. in stead work on local clone and pull
• [5] HZ2U4QEV no branch info available yet in scmdiff, so disable for now
• [6] ODWGRX32 check for revisions
• [7] BKOIYITR added some json responses
• [8] BK24VA6Q * for git inputs, check latest revision of branch (defaults to master for now), if there is change, only use input if last checkout was > hour ago.
• [9] TH674WKJ add log diff to compare logs to previous builds
• [*] OOQ2D3KC * Refactoring: move fetchInput out of hydra_scheduler into a separate

Change contents

• replacement in src/lib/Hydra/Controller/API.pm at line 224
  [3.690]→[3.690:756](∅→∅)
  − my $clonePath = scmPath . "/" . sha256_hex($uri.$branch);
  [3.690]

  [3.756]
  + my $clonePath = scmPath . "/" . sha256_hex($uri);
• replacement in src/lib/Hydra/Helper/AddBuilds.pm at line 312
  [4.124]→[2.0:61](∅→∅)
  − $clonePath = scmPath . "/" . sha256_hex($uri . $branch);
  [4.124]

  [4.179]
  + $clonePath = scmPath . "/" . sha256_hex($uri);