Merge git repositories with different base dir

Question

I have a project that was created from a tar ball and put under separate version control (at the time, the upstream did not use git). Now, upstream has migrated to git as well and I would like to reconnect the custom repository with upstream.

I assume it would be possible to add it as a remote and merge branches as shown in the diagram.

The problem is that the custom repository (loosely called fork here) has a different base dir. It includes a parent folder and holds the upstream file structure in /src.

How is it possible to merge these repositories so upstream can be tracked via git, without loosing the forks commit history?

Answer 1

In your custom repo do:

# Adapt structure to match upstream's structure
#
mkdir src
git mv repo_content.txt src
git commit -m 'adapt structure to upstream'

# Add remote to upstream repo
#
git remote add upstream [email protected]/repo
git fetch

# Do the merging,...
# (only master branch is considered here)
#
# Prepare to do some conflict solving, as merging without a
# common history may be a bit more "rough" when repo's
# diverted significantly.
#
git merge upstream/master