| Date: Sat, 5 Jan 2008 20:17:40 -0500 | |
| From: Sean <seanlkml@sympatico.ca> | |
| To: Miklos Vajna <vmiklos@frugalware.org> | |
| Cc: git@vger.kernel.org | |
| Subject: how to use git merge -s subtree? | |
| Abstract: In this article, Sean demonstrates how one can use the subtree merge | |
| strategy. | |
| Content-type: text/asciidoc | |
| Message-ID: <BAYC1-PASMTP12374B54BA370A1E1C6E78AE4E0@CEZ.ICE> | |
| How to use the subtree merge strategy | |
| ===================================== | |
| There are situations where you want to include contents in your project | |
| from an independently developed project. You can just pull from the | |
| other project as long as there are no conflicting paths. | |
| The problematic case is when there are conflicting files. Potential | |
| candidates are Makefiles and other standard filenames. You could merge | |
| these files but probably you do not want to. A better solution for this | |
| problem can be to merge the project as its own subdirectory. This is not | |
| supported by the 'recursive' merge strategy, so just pulling won't work. | |
| What you want is the 'subtree' merge strategy, which helps you in such a | |
| situation. | |
| In this example, let's say you have the repository at `/path/to/B` (but | |
| it can be a URL as well, if you want). You want to merge the 'master' | |
| branch of that repository to the `dir-B` subdirectory in your current | |
| branch. | |
| Here is the command sequence you need: | |
| ---------------- | |
| $ git remote add -f Bproject /path/to/B <1> | |
| $ git merge -s ours --no-commit Bproject/master <2> | |
| $ git read-tree --prefix=dir-B/ -u Bproject/master <3> | |
| $ git commit -m "Merge B project as our subdirectory" <4> | |
| $ git pull -s subtree Bproject master <5> | |
| ---------------- | |
| <1> name the other project "Bproject", and fetch. | |
| <2> prepare for the later step to record the result as a merge. | |
| <3> read "master" branch of Bproject to the subdirectory "dir-B". | |
| <4> record the merge result. | |
| <5> maintain the result with subsequent merges using "subtree" | |
| The first four commands are used for the initial merge, while the last | |
| one is to merge updates from 'B project'. | |
| Comparing 'subtree' merge with submodules | |
| ----------------------------------------- | |
| - The benefit of using subtree merge is that it requires less | |
| administrative burden from the users of your repository. It works with | |
| older (before Git v1.5.2) clients and you have the code right after | |
| clone. | |
| - However if you use submodules then you can choose not to transfer the | |
| submodule objects. This may be a problem with the subtree merge. | |
| - Also, in case you make changes to the other project, it is easier to | |
| submit changes if you just use submodules. | |
| Additional tips | |
| --------------- | |
| - If you made changes to the other project in your repository, they may | |
| want to merge from your project. This is possible using subtree -- it | |
| can shift up the paths in your tree and then they can merge only the | |
| relevant parts of your tree. | |
| - Please note that if the other project merges from you, then it will | |
| connect its history to yours, which can be something they don't want | |
| to. |