SHA-1 (Secure Hash Algorithm 1) produces a 160-bit (20-byte) hash value from a given input. Typically, SHA-1 hash is rendered in hexadecimal digits. SHA-1 produces a message digest (hash value) using similar principles as MD4, MD5 but generates a larger hash value.
Revision control systems such as Git, Mercurial, and Monotone use SHA-1, not for security, but to identify revisions and to ensure that the data has not changed due to accidental corruption. (Source - Wikipedia SHA-1.