Redmine

Under certain circumstances it may happen that revisions disappear from a git repository (i.e. when the repository is compacted / garbage collected after doing force pushes).

Redmine stores a prev_db_heads list in the repositories extra_info, which may contain hashes pointing to such no more existing objects. In this case, Repository#fetch_changesets will fail silently and not fetch anything, since the underlying git log command refuses to work when non existing revisions are given on the command line.

The attached patch was extracted from Planio and checks each entry in prev_db_heads, keeping only those that still exist.