What is the difference between a tree and a directory?

Question

I am a git novice trying to sort through the concepts and terms. The git glossary says a tree is equivalent to a directory and a directory is what you get with ls. Are they interchangeable terms? Or are "tree" and "directory" to be used in different contexts or to refer to separate (though related) things?

I had the same problem http://stackoverflow.com/questions/5917738/how-does-git-record-or-more-likely-represent-file-paths-and-names-for-its-blob - The commit tree structure is/does match the directory structure of the files contained in the commit, but excludes 'empty' directories with nothing to track. Checking out a branch will create any needed directories, but won't delete any. — Philip Oakley, Jun 04 '11 at 20:01

score 3 · Answer 1 · answered Jun 04 '11 at 03:30

In Git terminology, a "tree" is a hierarchical structure of files and directories. This is (purposefully) very similar to a directory in a filesystem.

A Git commit object contains a reference to a tree object, which is the state of all files at the time of that commit.

score 3 · Accepted Answer · answered Jun 04 '11 at 07:43

3

The short answer: yes, a tree is a directory and a directory is a tree.

The long answer: A tree is an object that contains a list of blobs, the names to attach to the blobs, and other trees and the names to attach to them. http://book.git-scm.com/1_the_git_object_model.html has a pretty good explanation of the different object types in the git model; I would suggest reading it!

answered Jun 04 '11 at 07:43

clee

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Yes, understanding that the tree references blobs was key. – user7797 Jun 05 '11 at 00:42

OnesimusUnbound · Answer 3 · 2011-06-04T03:49:13.893

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edited Jun 04 '11 at 03:49

answered Jun 04 '11 at 03:38

OnesimusUnbound

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The diagrams in the second link were very helpful. – user7797 Jun 05 '11 at 00:31
Thanks. Personally, I was able to understand git's object model through the illustrated diagram. – OnesimusUnbound Jun 06 '11 at 02:22

score -1 · Answer 4 · answered Jun 04 '11 at 03:33

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To put it simply, the "tree" refers to the snapshot of the entire repository state at that moment in time (like what you've got for your current code [which is also known as HEAD], of the repository when the currently checked-out commit was made, etc.)

Directory is just referring to a filesystem directory.

answered Jun 04 '11 at 03:33

damianb

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I scare myself with my parenthesis layering sometimes. – damianb Jun 04 '11 at 03:34
Not strictly true since a tree contains other trees, which themselves may also belong to trees from previous (and future) commits. – siride Jun 04 '11 at 04:09
The tree for some directory and the tree for the same directory in other commit may be the same (same SHA1). So a tree may not represent the whole directory and it has nothing to do with time (commits do). – svick Jun 04 '11 at 21:35

What is the difference between a tree and a directory?

4 Answers4