A Directory Hasher
dasher is a small utility intended to allow you to condense the "status" of an entire
directory tree down to a single hash digest. Thus, you can tell that something has
changed in the tree (but not what has changed) if the hash has changed.
dasher is easiest to install via Cargo
$ cargo install dasher
You can, of course, also clone this repository and cargo build/cargo run the code
that way.
dasher currently does not have a CLI, but it is in the works.
The hashing scheme is, in essence, generating a Merkle tree, but with extra steps. Each node in the directory tree has its name hashed, then its contents, then those hashes are concatenated with a separator byte based on the node's type, and that data is hashed again to generate the node's hash. This process is repeated, from the bottom up in the directory tree, until all nodes have been hashed and a final hash for the entire directory can be returned.
For normal files, the node hash is simply:
hash(hash(name) + byte + hash(content))
For directories, the node hash includes arbitrarily many content hashes, one per
sub-node:
hash(hash(name) + byte + hash(content_1) + byte + hash(content_2) + ... + byte + hash(content_n))
Finally, for symlinks, the link isn't followed. Instead, the content hash is the
hash of the path to the file the link points to.
hash(hash(name) + byte + hash(path))
Traversal of the directory is not recursive --- rather, the process starts with the leaves in the lexicographically "first" directory. For example, in the directory ``` .git ├── COMMIT_EDITMSG ├── config ├── info │ └── exclude └── logs ├── HEAD └── refs ├── heads │ ├── add-cli │ ├── dh-main │ └── main └── remotes └── origin └── main
``
the first item to be hashed would beinfo/exclude, followed by the directory hash of
theinfodirectory. After that,logs/refs/heads/*would be hashed, then
logs/refs/heads/remotes/origin/main, thenlogs/refs/heads/remotes/originas a
directory, thenlogs/refs/heads/remotesas a directory, then finally climbing back up
to hashlogs/refs`, since both its sub-directories have been hashed.
In a way, I guess you could consider this as being recursive, but it is not implemented recursively.
dasher is licensed under either of
at your option.