Menu
Git stores individual objects in .git/objects/ab/cdefgh... where ab is the first byte of the SHA1 digest.
However, pack files don't follow the same naming policy, and I can find no documentation on how it is named. Any insights?
611
The packfile is a single file containing the contents of all the objects that were removed from your filesystem. The index is a file that contains offsets into that packfile so you can quickly seek to a specific object.
objects − This folder represents an object database of Git. config − This is the local configuration file. refs − This folder stores information about tags and branches.
Blob is an abbreviation for “binary large object”. When we git add a file such as example_file. txt , git creates a blob object containing the contents of the file. Blobs are therefore the git object type for storing files.
There are 3 main types of objects that git stores: Blob: This object as we have seen above stores the original content. Tree: This object is used to store directories present in our project. Commit: This object is created whenever a commit is made and abstracts all the information for that particular commit.
The pack files are kept in objects/pack, which is documented in gitrepository layout. Within this directory, they are stored as pairs of an index file and the pack file itself, called, for example:
pack-a862cfa8b080773290073999c800a2e655ef9b5d.idx
pack-a862cfa8b080773290073999c800a2e655ef9b5d.pack
How the SHA1sum in those filenames is calculated is explained in the git-pack-objects documentation (my emphasis):
Write into a pair of files (.pack and .idx), using <base-name> to determine the name of the created file. When this option is used, the two files are written in <base-name>-<SHA1>.<pack,idx> files. <SHA1> is a hash of the sorted object names to make the resulting filename based on the pack content, and written to the standard output of the command.
The object names are the SHA1sums of the objects within the pack file.
135
The answer is either "the SHA-1 hash of the entire pack file, minus the last 20 bytes", or "a hexadecimal digest of the last 20 bytes" (both are equivalent).
The last 20 bytes of the file is the "trailer checksum" which itself is a SHA-1 hash of the entirety of the file (minus the last 20 bytes).
This was changed in 2013 (previously it was the SHA-1 sum of all the hashes in the file). Note that the documentation now simply reads " is a hash based on the pack content". The author explicitly does not guarantee how the SHA-1 is calculated (from the commit log: "Hopefully this will discourage readers from depending on the old or the new calculation.").
40
If you love us? You can donate to us via Paypal or buy me a coffee so we can maintain and grow! Thank you!
Donate Us With
