如何加快寻找上市git存储库？

问题描述

我想查找位于某个目录中的所有 git 存储库，而不是其子目录，例如）来测试 -depth 更新 -depth 2 ）未在。这可能是一个OSX扩展。不要使用它！

使用 -mindepth 2 -maxdepth 2 来代替，正如@ hek2mgl在。

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h3> OSX特定的

当<$ $时，似乎OSX版本的 find 不必要地下降到比2级更深的目录使用c $ c> -depth 2 （但这是正确的行为，见下文）。

你可以告诉它不要在 -depth 2 之后立即加上 -prune 如果你把它放在别的地方，就会有任何影响）：

  find〜/ repo -depth 2 -prune -type d -name。 git 
  

一些基准：

  $ time（find。-depth 4 -prune -type d -name .git | wc -l）
 20 
 
 real 0m0.064s 
用户0m0.009s 
 sys 0m0.046s 
  

已移动 -prune 在t他结束了，它突然需要很多时间才能运行：

  $ time（find。 -depth 4 -type d -name .git -prune | wc -l）
 20 
 
 real 0m12.726s 
 user 0m0.325s 
 sys 0m9.298s 
  

备注

第二个想法是（仔细阅读 man找到） -depth 2 不需要 find 在超过两个的目录中停止递减水平。它可以是一个更复杂的条件的一部分，它需要 -depth 2 或别的东西（fe find。-depth 2 - 或者--name .git ）。

要强制停止下降超过两个级别，您必须使用 -maxdepth 2 或 -depth 2 -prune 。

• -maxdepth 告诉它不要超过两层;
  
• -depth 2 -prune 告诉它会停止下降到子目录中，如果被检查的目录是两层深的。

它们有相同的行为，选择一个或另一个是优先事项。我会选择 -maxdepth 2 ，因为它更清晰。 结论 b $ b

因为 -depth 2 不可移植，所以最终的命令应该是这样的：

  find〜/ repo -mindepth 2 -maxdepth 2 -type d -name'.git'-print 
  

感谢@ hek2mgl提及兼容性问题。

I want to find all git repositories lying in some directory, but not its subdirectories, say ~/repo. Two simple approaches are

find ~/repo -depth 2 -type d -name '.git' | while read repo …

or

for repo in ~/repo/*/.git …

The version using find is magnitudes slower than the one with the globbing pattern. I am very surprised by this, because there is no real reason why one method would need more system calls than the other to gather its informations. I tried a smarter version of the find invocation

find ~/repo -depth 3 -prune -o -depth 2 -type d -name '.git' -print | while read repo …

without any noticeable improvement. Unfortunately I was not able to trace system calls to figure out how find is working here.

What explains the huge speed difference between these two methods? (The shell is /bin/sh which I believe to be some obsolete version of bash.)

解决方案

Update: the test -depth with arguments (-depth 2) is not specified in the documentation of GNU find. It is probably an OSX extension. Don't use it!

Use -mindepth 2 -maxdepth 2 instead, as suggested by @hek2mgl in their answer.

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OSX specific

It seems the OSX version of find unnecessarily descends into directories deeper than 2 levels when -depth 2 is used (but this is the correct behaviour, see below).

You can tell it to not do that by adding -prune immediately after -depth 2 (it seems it doesn't have any effect if you put it somewhere else):

find ~/repo -depth 2 -prune -type d -name .git

Some benchmarks:

$ time (find . -depth 4 -prune -type d -name .git | wc -l)
      20

real 0m0.064s
user 0m0.009s
sys  0m0.046s

Moved -prune at the end and it suddenly needs a lot of time to run:

$ time (find . -depth 4 -type d -name .git -prune | wc -l)
      20

real 0m12.726s
user 0m0.325s
sys  0m9.298s

Remarks

On a second thought (and after a closer reading of man find) -depth 2 does not require find to stop descending in directories deeper than two levels. It can be part of a more complex condition that requires -depth 2 or something else (f.e. find . -depth 2 -or -name .git).

To force it to stop descending more than two levels you must use either -maxdepth 2 or -depth 2 -prune.

• -maxdepth tells it to not go deeper than two levels;
• -depth 2 -prune tells it to stop descending into subdirectories if the directory under examination is two levels deep.

They have equivalent behaviour, choosing one or another is a matter of preference. I would choose -maxdepth 2 because it is more clear.

Conclusion

Because -depth 2 is not portable, the final command should be like:

find ~/repo -mindepth 2 -maxdepth 2 -type d -name '.git' -print

Thanks @hek2mgl for mentioning about the compatibility issue.

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