How do you merge two Git repositories?

Question

Consider the following scenario:

I have developed a small experimental project A in its own Git repo. It has now matured, and I\'d like A to be part of larger projec

Answer 1

A single branch of another repository can be easily placed under a subdirectory retaining its history. For example:

git subtree add --prefix=rails git://github.com/rails/rails.git master

This will appear as a single commit where all files of Rails master branch are added into "rails" directory. However the commit's title contains a reference to the old history tree:

Add 'rails/' from commit

Where is a SHA-1 commit hash. You can still see the history, blame some changes.

git log 
git blame  -- README.md

Note that you can't see the directory prefix from here since this is an actual old branch left intact. You should treat this like a usual file move commit: you will need an extra jump when reaching it.

# finishes with all files added at once commit
git log rails/README.md

# then continue from original tree
git log  -- README.md

There are more complex solutions like doing this manually or rewriting the history as described in other answers.

The git-subtree command is a part of official git-contrib, some packet managers install it by default (OS X Homebrew). But you might have to install it by yourself in addition to git.