Subtree Merge
There are times when submodules are not adequate for the task at hand. For example, blending multiple repos together into one single repo while still maintaining the history of each repo. To do this, the subtree merge strategy is a better solution.
Setting up and doing the first merge
For this example, we’ll make an empty “parent” repo and some other repos into it as subpaths.
First, set up an empty repo for our example:
[tekkub@tekBook: ~/tmp master*] $ mkdir test [tekkub@tekBook: ~/tmp master*] $ cd test [tekkub@tekBook: ~/tmp/test master*] $ git init Initialized empty Git repository in /Users/tekkub/tmp/test/.git/ [tekkub@tekBook: ~/tmp/test master#] $ touch .gitignore [tekkub@tekBook: ~/tmp/test master#] $ git add .gitignore [tekkub@tekBook: ~/tmp/test master#] $ git commit -m "initial commit" [master (root-commit) 3146c2a] initial commit 0 files changed, 0 insertions(+), 0 deletions(-) create mode 100644 .gitignore
Now we’ll subtree-merge the repo tekkub/cork into the repo at cork/
[tekkub@tekBook: ~/tmp/test master] $ git remote add -f cork git://github.com/tekkub/cork.git Updating cork warning: no common commits remote: Counting objects: 1732, done. remote: Compressing objects: 100% (750/750), done. remote: Total 1732 (delta 1086), reused 1558 (delta 967) Receiving objects: 100% (1732/1732), 528.19 KiB | 621 KiB/s, done. Resolving deltas: 100% (1086/1086), done. From git://github.com/tekkub/cork * [new branch] lastbuffed -> cork/lastbuffed * [new branch] lock_n_mount -> cork/lock_n_mount * [new branch] master -> cork/master * [new branch] nothing_to_see_here -> cork/nothing_to_see_here [tekkub@tekBook: ~/tmp/test master] $ git merge -s ours --no-commit cork/master Automatic merge went well; stopped before committing as requested [tekkub@tekBook: ~/tmp/test master|MERGING] $ git read-tree --prefix=cork/ -u cork/master [tekkub@tekBook: ~/tmp/test master+|MERGING] $ git commit -m "Subtree merged in cork" [master fe0ca25] Subtree merged in cork
Next, we’ll merge in tekkub/panda into the path panda/
[tekkub@tekBook: ~/tmp/test master] $ git remote add -f panda git://github.com/tekkub/panda.git Updating panda warning: no common commits remote: Counting objects: 974, done. remote: Compressing objects: 100% (722/722), done. remote: Total 974 (delta 616), reused 399 (delta 251) Receiving objects: 100% (974/974), 189.56 KiB, done. Resolving deltas: 100% (616/616), done. From git://github.com/tekkub/panda * [new branch] master -> panda/master * [new branch] transmute -> panda/transmute [tekkub@tekBook: ~/tmp/test master] $ git merge -s ours --no-commit panda/master Automatic merge went well; stopped before committing as requested [tekkub@tekBook: ~/tmp/test master|MERGING] $ git read-tree --prefix=panda/ -u panda/master [tekkub@tekBook: ~/tmp/test master+|MERGING] $ git commit -m "Subtree merged in panda" [master 726a2cd] Subtree merged in panda
Finally, we’re going to merge the subpath modules/ from tekkub/cork into cork2/
tekkub@iSenberg ~/tmp/test master $ git merge -s ours --no-commit cork/master Automatic merge went well; stopped before committing as requested tekkub@iSenberg ~/tmp/test master|MERGING $ git read-tree --prefix=cork2/ -u cork/master:modules tekkub@iSenberg ~/tmp/test master+|MERGING $ git commit -m "Subtree merged in cork/modules" [master f240057] Subtree merged in cork/modules
Pulling in changes
If the merged repo changes in the future, you can pull in its changes by simply using the -s subtree flag:
[tekkub@tekBook: ~/tmp/test master] $ git pull -s subtree panda master
