Stages a staged file in git?

Question

I'm using git to manage my project. And I'm confused with the workflow of git when staging a file.

If I staged files and forgot commit and then I modify that files and stages again and commit, how can I roll back to first staged ?

Answer 1

As described in "Git Internals - Git Objects", each time you change the content of a file, and add it to the cache, you do a:

git hash-object -w test.txt

That stores it to the object stored.

I just did two git add consecutively for one file, followed by a:

C:\Users\VonC\prog\go\src\github.com\VonC\asciidocgo\.git>gfind -mmin -10 -print
.
./index
./objects/4f
./objects/4f/76d586459ec6ffc42257bb4c61d5422051cb10
./objects/61
./objects/61/24401794e7fee613f5a56593a0a8a059b2627a

(Note the -mmin parameter to find files modified since the last 10 minutes only)

I could have listed those same sha1 after each git add with a:

git rev-parse :0:abstractNode_test.go

See git rev-parse (and "What does git rev-parse do?"): adding a file in the index is stage 0 only (stage 1, 2 and 3 are used during a merge to record, still in the index, the common ancestor, source and destination versions).

If I store the content of those two blobs:

C:\Users\VonC\prog\go\src\github.com\VonC\asciidocgo>
git cat-file -p 4f76d586459ec6ffc42257bb4c61d5422051cb10 > a
git cat-file -p 6124401794e7fee613f5a56593a0a8a059b2627a > b

(Note how I concatenate the '4f/' part of the blob path with the rest of the path in order to obtain the full sha1)

The diff between a and b does give me the additional bit I added to the index for that same file.

---

torek also mentions in the comments:

Another (I think easier) way: git fsck --lost-found.
Dangling blob objects wind up in .git/lost-found/other/ and are already cat-file -p-ed.

You would indeed found all the previous git add you did before the final one which ended up committed.
In my case, only one showed up:

C:\Users\VonC\prog\go\src\github.com\VonC\asciidocgo\.git\lost-found\other>dir
 Volume in drive C has no label.
 Volume Serial Number is D866-48E1

 Directory of C:\Users\VonC\prog\go\src\github.com\VonC\asciidocgo\.git\lost-found\other

25/01/2014  17:31    <DIR>          .
25/01/2014  17:31    <DIR>          ..
25/01/2014  17:31            16 873 4f76d586459ec6ffc42257bb4c61d5422051cb10