Since upgrading to the most current Git plug-in, we are seeing a recurring issue where the slave runs out of java heap while polling.

After some experimentation, we determined that the failure occurs after the git plug-in detects a change on the target branch, if that change is the result of a merge from another branch. In this case, the plug-in executes the following command:
git show --no-abbrev --format=raw -M --raw 2788f90d10b251842a194d301c7badc71d87a279..bee56170f462e3c62031c2b9206bb425d3fb09ff
This command runs for three minutes (or so) and then the slave kills it. I am attaching the output as displayed in the Git Polling Log.

Triggering the build manually causes the build to run, and then everything is hunky-dory until the next merge goes in.

We have tried both raising and lowering the Xmx value, to no effect.