我目前有一个包含多个项目的庞大git仓库，每个项目都在其自己的子目录中。我需要将其拆分成单独的仓库，每个项目在其自己的仓库中。
我尝试了git filter-branch --prune-empty --subdirectory-filter PROJECT master
然而，许多项目目录在它们的生命周期中经历了几次重命名，而git filter-branch不会跟随重命名，因此提取出的仓库实际上没有任何历史记录超过最后一次重命名。
如何有效地从一个庞大的git仓库中提取一个子目录，并跟踪该目录的所有重命名到过去？
git filter-branch --prune-empty --index-filter '
# Delete files which are NOT needed
git ls-files -z | egrep -zv "^(NAME1|NAME2|NAME3)" |
xargs -0 -r git rm --cached -q
# Move files to root directory
git ls-files -s | sed -e "s-\t\(NAME1\|NAME2\|NAME3\)/-\t-" |
GIT_INDEX_FILE=$GIT_INDEX_FILE.new \
git update-index --index-info &&
( test ! -f "$GIT_INDEX_FILE.new" \
|| mv -f "$GIT_INDEX_FILE.new" "$GIT_INDEX_FILE" )
'
删除所有在三个目录NAME1、NAME2或NAME3之外的文件（其中一个项目在其生命周期内被重命名为NAME1 -> NAME2 -> NAME3）。
将这三个目录中的所有内容移动到仓库的根目录。
我需要测试是否存在"$GIT_INDEX_FILE.new"，因为从svn导入到git会创建没有任何文件（只有目录）的提交。仅在最初使用'git svn clone'创建存储库时需要。
我有一个非常大的代码仓库，需要提取其中的一个文件夹；即使使用 --index-filter 预计也需要8小时才能完成。以下是我采用的方法：
old-name and new-name.For each name:
$ git checkout master
$ git checkout -b filter-old-name
$ git filter-branch --subdirectory-filter old-name
This will give you several disconnected branches, each containing history for one of the names.
The filter-old-name branch should end with the commit which renamed the folder, and the filter-new-name branch should begin with the same commit. (The same applies if there was more than one rename: you'll wind up with an equivalent number of branches, each with a commit shared with the next one along.) One should delete everything and the other should recreate it again. Make sure that these two commits have identical contents; if they don't, the file was modified in addition to being renamed, and you will need to merge the changes. (In my case I didn't have this problem so I don't know how to solve it.)
An easy way to check this is to try rebasing filter-new-name on top of filter-old-name and then squashing the two commits together: git should complain that this produces an empty commit. (Note that you will want to do this on a spare branch and then delete it: rebasing deletes the Committer information from the commits, thus losing some of the history you want to keep.)
The next step is to graft the two branches together, skipping the two commits which renamed the folder. (Otherwise there will be a weird jump where everything is deleted and recreated.) This involves finding the full SHA (all 40 characters!) of the two commits and putting them into git's info, with the new name branch's commit first, and the old name branch's commit second.
$ echo $NEW_NAME_SECOND_COMMIT_SHA1 $OLD_NAME_PENULTIMATE_COMMIT_SHA1 >> .git/info/grafts
If you've done this right, git log --graph should now show a line from the end of the new history to the start of the old history.
This graft is currently temporary: it is not yet part of the history, and won't follow along with clones or pushes. To make it permanent:
$ git filter-branch
This will refilter the branch without trying to make any further changes, making the graft permanent (changing all of the commits in the filter-new-name branch). You should now be able to delete the .git/info/grafts file.
filter-new-name 分支上拥有文件夹两个名称的所有历史记录。然后，您可以使用此单独的代码库，或将其合并到另一个代码库中，或者按照您的意愿处理这些历史记录。git filter-branch --prune-empty --tree-filter YOURSCRIPT。然后，您的脚本将必须识别正确的文件夹（也许是其中一个特定文件的名称，或者您可能拥有项目过去所有名称的列表），删除其他所有内容并将文件夹内容上移一级。--index-filter更快地实现相同的效果，但编写该脚本会更加复杂。您将必须使用git修改索引的命令而不是文件系统修改命令。
git-filter-repo的解决方案，因为现在它已经被推荐用来替代git-filter-branch。 - Martin Thøgersen