RE: merge-base not working as expected when base is ahead

Dear Git,

git merge-base --fork-point "master" not working if master is already newer then my current branch. Very oddly it seems to work whenever you had the expected commit checked out previously - what made it very tricky to detect this problem.

Example:
 - Clone "https://github.com/jekelhart/GitInfoTry"
 - Switch to branch "v1.0.0"
 - git merge-base --fork-point "master"
   - or: git merge-base --fork-point "origin/master" 
 - expected result: fork point "fbb1db34c6317a6e8b319c1ec261e97ca1672c22"
 - but result is empty

In the repo where we created this example tree in the first place the command returned the expected fork point. If you clone it new and fresh it does not return any result anymore.

Works, however, on branch "v2.0.0". Assumption: because "master" is older.(?) I think it works locally because the command uses the reflog in addition(!), however, it should work without the local reflog as well. (since the history was not modified in any way)

BR, Jakob