As we learned previously, the add command creates the blob, tree, and commit objects; however, they are also created when we run the commit command. We can view these objects using the cat-file command, as we saw in the previous recipe:
$ git cat-file -p HEAD tree 162201200b5223d48ea8267940c8090b23cbfb60 parent 13dcada077e446d3a05ea9cdbc8ecc261a94e42d author John Doe <[email protected]> 1524163792 +0200 committer John Doe <[email protected]> 1524163792 +0200
Making changes to another file.
The root-tree object from the commit is as follows:
$ git cat-file -p HEAD^{tree}
100644 blob f21dc2804e888fee6014d7e5b1ceee533b222c15 README.md
040000 tree abc267d04fb803760b75be7e665d3d69eeed32f8 a_sub_directory
100644 blob 35d31106c5d6fdb38c6b1a6fb43a90b183011a4b another-file.txt
100644 blob 92f046f17079aa82c924a9acf28d623fcb6ca727 cat-me.txt
100644 blob bb2fe940924c65b4a1cefcbdbe88c74d39eb23cd hello_world.c
From the previous recipe, we know that the SHA-1 of the root tree was 34fa038544bcd9aed660c08320214bafff94150b and the SHA-1 of the another-file.txt file was b50f80ac4d0a36780f9c0636f43472962154a11a, and, as expected, they changed in our latest commit when we updated the another-file.txt file. We added the same file, another-file.txt, twice before we created the commit, recording the changes to the history of the repository. We also learned that the add command creates a blob object when called. So, in the Git database, there must have been an object similar to the content of another-file.txt the first time we added the file to the staging area. We can use the git fsck command to check for dangling objects—that is, objects that are not referred to by other objects or references:
$ git fsck --dangling Checking object directories: 100% (256/256), done. dangling blob ad46f2da274ed6c79a16577571a604d3281cd6d9
Let's check the content of the blob using the following command:
$ git cat-file -p ad46f2da274ed6c79a16577571a604d3281cd6d9 This is just another file Another line
The blob was, as expected, similar to the content of another-file.txt when we added it to the staging area the first time.
The following diagram describes the tree stages and the commands used to move between the stages:
