Commits on Aug 5, 2019

1. commit-graph: fix bug around octopus merges …

   In 1771be9 "commit-graph: merge commit-graph chains" (2019-06-18),
   the method sort_and_scan_merged_commits() was added to merge the
   commit lists of two commit-graph files in the incremental format.
   Unfortunately, there was an off-by-one error in that method around
   incrementing num_extra_edges, which leads to an incorrect offset
   for the base graph chunk.
   
   When we store an octopus merge in the commit-graph file, we store
   the first parent in the normal place, but use the second parent
   position to point into the "extra edges" chunk where the remaining
   parents exist. This means we should be adding "num_parents - 1"
   edges to this list, not "num_parents - 2". That is the basic error.
   
   The reason this was not caught in the test suite is more subtle.
   In 5324-split-commit-graph.sh, we test creating an octopus merge
   and adding it to the tip of a commit-graph chain, then verify the
   result. This _should_ have caught the problem, except that when
   we load the commit-graph files we were overly careful to not fail
   when the commit-graph chain does not match. This care was on
   purpose to avoid race conditions as one process reads the chain
   and another process modifies it. In such a case, the reading
   process outputs the following message to stderr:
   
   	warning: commit-graph chain does not match
   
   These warnings are output in the test suite, but ignored. By
   checking the stderr of `git commit-graph verify` to include
   the expected progress output, it will now catch this error.
   
   Signed-off-by: Derrick Stolee <dstolee@microsoft.com>

   

   derrickstolee committed Aug 5, 2019
   Configuration menu

   • View commit details
   • Copy full SHA for 6e913ac
   • Browse repository at this point

   Copy the full SHA

   6e913ac View commit details

   Browse the repository at this point in the history