how does stashing work in git - internals

Question

Where can I get informatin about how git stashing works internally? I'm interested in detailed explanation similiar to the one about git objects in the 9.2 Git Internals - Git Objects of git-scm book.

EDIT: I'm updating my question based on the information that I received from that link. Is my logic described below correct?
HEAD is on the branch br1. The last commit 'br1-c0' on that branch had the following tree:

somefile.txt (text inside - 'some text') anotherfile.txt

I've modified somefile.txt to have 'updated text' as text inside. I'm stashing changes:

1) one commit is created, which has the following tree: somefile.txt (text inside - 'updated text') anotherfile.txt AND has link to commit 'br1-c0' and state of file index.

2) the working tree is reverted to 'br1-c0' commit.

Answer 1

Git is open source so source code ;) (or google)

In any case the stashes are list of commits. You can see how they are constructed by creating a stash:

 # git stash --keep-index
 # git stash list
 stash@{0}: WIP on master: dafe337 sss
 # git log 'stash@{0}' | cat
 commit 7f86a90fb4e57590d6fe5026b7408306a757132a
 Merge: dafe337 2881ede
 Author: Maciej Piechotka <[email protected]>
 Date:   Fri Aug 30 09:27:10 2013 +0200

     WIP on master: dafe337 sss

 commit 2881ede55d619570a82bb7312257c4e43bd3b334
 Author: Maciej Piechotka <[email protected]>
 Date:   Fri Aug 30 09:27:10 2013 +0200

     index on master: dafe337 sss

 commit dafe33716c2e5aee994612c88d8142f1163c624e
 Author: Maciej Piechotka <[email protected]>
 Date:   Fri Aug 30 09:25:40 2013 +0200

     sss

Sss is first commit (HEAD) while the rest two commits is the save of current index (staged changes) and the merge contains unstaged changes:

% git show 2881ede55d619570a82bb7312257c4e43bd3b334
commit 2881ede55d619570a82bb7312257c4e43bd3b334
Author: Maciej Piechotka <[email protected]>
Date:   Fri Aug 30 09:27:10 2013 +0200

    index on master: dafe337 sss

diff --git a/test.c b/test.c
index b9a1dd0..7beafd5 100644
--- a/test.c
+++ b/test.c
@@ -1 +1,2 @@
 dddd
+fff
% git show 7f86a90fb4e57590d6fe5026b7408306a757132a
commit 7f86a90fb4e57590d6fe5026b7408306a757132a
Merge: dafe337 2881ede
Author: Maciej Piechotka <[email protected]>
Date:   Fri Aug 30 09:27:10 2013 +0200

    WIP on master: dafe337 sss

diff --cc test.c
index b9a1dd0,7beafd5..551a609
--- a/test.c
+++ b/test.c
@@@ -1,1 -1,2 +1,3 @@@
  dddd
+ fff
++ggg

Now the list of stashes is an existing structure - reflog (n.b. useful structure on its own) and the name is... stash. So stashes are implemented de-facto as a branch with moving head and what we are interested in is reflog. To make it more interesting I created a second stash which created commit 0dee308c461955e13a864c9a904a69d611e82730.

% git reflog stash | cat
7f86a90 stash@{0}: WIP on master: dafe337 sss
% cat .git/refs/stash
0dee308c461955e13a864c9a904a69d611e82730
% cat .git/logs/refs/stash
0000000000000000000000000000000000000000 7f86a90fb4e57590d6fe5026b7408306a757132a Maciej Piechotka <[email protected]> 1377847630 +0200 WIP on master: dafe337 sss
7f86a90fb4e57590d6fe5026b7408306a757132a 0dee308c461955e13a864c9a904a69d611e82730 Maciej Piechotka <[email protected]> 1377847983 +0200 WIP on master: dafe337 sss