I have a Git repository in a folder called XXX, and I have second Git repository called YYY.
I want to import the XXX repository into the YYY repository as a subdirectory named ZZZ and add all XXX's change history to YYY.
Folder structure before:
├── XXX
│ ├── .git
│ └── (project files)
└── YYY
├── .git
└── (project files)
Folder structure after:
YYY
├── .git <-- This now contains the change history from XXX
├── ZZZ <-- This was originally XXX
│ └── (project files)
└── (project files)
Can this be done, or must I resort to using sub-modules?
Probably the simplest way would be to pull the XXX stuff into a branch in YYY and then merge it into master:
In YYY:
git remote add other /path/to/XXX
git fetch other
git checkout -b ZZZ other/master
mkdir ZZZ
git mv stuff ZZZ/stuff # repeat as necessary for each file/dir
git commit -m "Moved stuff to ZZZ"
git checkout master
git merge ZZZ --allow-unrelated-histories # should add ZZZ/ to master
git commit
git remote rm other
git branch -d ZZZ # to get rid of the extra branch before pushing
git push # if you have a remote, that is
I actually just tried this with a couple of my repos and it works. Unlike Jörg's answer it won't let you continue to use the other repo, but I don't think you specified that anyway.
Note: Since this was originally written in 2009, git has added the subtree merge mentioned in the answer below. I would probably use that method today, although of course this method does still work.