ppg-is-ancestor

   1 #!/bin/bash
   2 #
   3 # emulates git merge-base --is-ancestor
   4 # until git >= 1.8 is prevalent
   5 #
   6 ## Check if the first <commit> is an ancestor of the second <commit>,
   7 ## and exit with status 0 if true, or with status 1 if not.
   8 ## Errors are signaled by a non-zero status that is not 1.
   9
  10 PARENT=$1
  11 CHILD=$2
  12
  13 # they may be symbolic, a refname or a pointer to a full tag,
  14 # make sure we resolve to sha1 of the commit
  15 PARENT=$(git rev-parse --revs-only ${PARENT}^{commit} ) || exit 1
  16 CHILD=$(git rev-parse --revs-only ${CHILD}^{commit} ) || exit 1
  17
  18 MB=$(git merge-base $PARENT $CHILD) || exit 1
  19
  20 if [ "$MB" = "$PARENT" ]; then
  21         exit 0
  22 fi
  23 exit 1