Hash trees are used in the IPFS, Btrfs and ZFS file systems, BitTorrent protocol, Dat protocol, Apache Wave protocol, Git and Mercurial distributed revision control systems, the Tahoe-LAFS backup system, the Bitcoin and Ethereum peer-to-peer networks, the Certificate Transparency framework, and a number of NoSQL systems like Apache Cassandra, Riak and Dynamo.
Mostly the reverse, if you need to relate them a blockchain is a degenerate Git (history, which is a subset of Git itself):
A Git history is a DAG[0] (each commit can have multiple parents) and beyond that a polytree (it can have multiple roots); while a blockchain is an arborescence[2] (there's a single root — the "genesis block"; and each block can only have a single parent).
Further, beyond the technicalities blockchains are generally very linear (the side-chains tend to be pretty short, forks aside) while Git repositories can be extremely broad (have lots of concurrent branches).
The answer depends entirely on definition. What properties of bitcoin are essential to a blockchan vs which properties are simply how bitcoin happens to use a blockchain?
If blockchain just means the Merkle tree, then yes.
If it means Merkle tree + a computational consensus system for adding nodes, then no.
Short answer, yes. The current commit includes the hash of its parent(s), so its own hash reflects the whole history, and one can not change the history without also changing the current hash. Just like a block contains the hash of the previous block.
That's a Merkle Tree. A blockchain is an application of a Merkle tree in which each node contains transaction data, and a majority of clients agree that the longest chain of blocks is the correct one.
Git also uses a Merkle-DAG, but it is not a blockchain.
But this ‘definition’ seems to needlessly tie the definition to the kind of data you are transmitting. And if that were the case, couldn’t a software diff be considered a kind of transaction?
