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We know that the git commit submit command is based on the staging area, and if you modify the contents of the workspace, you must use git add / git rm, etc., to add the changes to the staging area, otherwise you cannot commit.

There is an index file in the .git directory, which is the register file, which is updated when we use the modify staging command.

1. Contents of the temporary storage area

What is stored in the staging area is a reference to the git blob object and some path information for the blob object. We can use git ls-files-- stage

$git ls-files-- stage100644 72943a16fb2c8f38f9dde202b7a70ccc19c52f34 0 fas.txt100644 f910c723c9bbc92b2d61c094859e68bbf7215ab2 0 hello.txt100644 b08a2810d8a4542f350f650435f506c6c81ca9b2 0 src/hello.txt2. Analysis of the two-tier system of temporary storage area

When we use notepad++ to open the file in hexadecimal format, the contents are as follows:

The corresponding format is:

| | 0 | 4 | 8 | C | |-| |-|-| -|-| 0 | DIRC | Version | File count | ctime. | 0 |. | mtime | device | 2 | inode | mode | UID | GID | 2 | File size | Entry SHA-1. | 4 |. | | Flags | Index SHA-1... | 4 |... | |

44 49 52 43: DIRC. Fixed header 00 00 00 02: format version 00 00 00 03: the number of register files, we have three

The following is a list of information for each file. If there are multiple files, read them in the following order

Ctime: eight digits, which is the time when the file was created. Mtime: occupies eight bits, is the file modification time of four bytes of device,inode,mode,UID,GID. These attributes are used to better detect whether the file has changed without comparing the contents of the file. File size: a file size of four bytes. Entry SHA-120: the ID (SHA-1) of the byte blob object, pointing to the blob object of git. The Flag object occupies four bytes, or 32bit bits. The first bit bit is the valid flag and the second bit bit is the extended flag bit. The third and fourth bit bits represent the status of the scratch block, mainly the state of the merge. 0: normal file status does not merge conflict 1: base 2: ours 3: theirs. The fifth to sixteenth bit bits indicate the path length of the file. For example, if the value is 0007, then the next seven bytes are path information. The next two bytes exist only if the second bit is an extension. File name and path information: its length depends on the value of the fifth to sixteenth bit bits in the Flag object. The path information is encoded by utf-8 (default, it is best not to modify it). For example, if the saved path is "temporary directory / hello.txt", the binary result is "e4 b8 b4 b4 e6 97 b6 e7 9b ae e5 bd 95 2f 68 65 6c 6f 6f 2e 74 78 74". String s = "temporary directory / hello.txt"; byte [] bytes = s.getBytes ("utf-8"); for (byte b: bytes) {System.out.print (Integer.toHexString (b & 0xFF) + "") Output: e4 b8 b4 e6 97 b6 e7 9b ae e5 bd 95 2f 68 65 6c 6f 6f 2e 74 78 74 followed by 00 of 1-8 bytes, this is necessary for the number of index contents of the file to be a multiple of 8, at least 1, if the content of the file happens to be a multiple of 8, then there will be 8 00 bytes.

The last 20 digits are the checksum of the above.

Reference: https://stackoverflow.com/questions/4084921/what-does-the-git-index-contain-exactly

3. Why is there a temporary storage area?

Submit in segments. You may not want to submit changes to the entire workspace. If you add a temporary storage area, you can submit them in segments.

Https://www.zhihu.com/question/19946553

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