This adds a set of functions to abstract over SHA1Init, SHA1Update, SHA1Final, their respective SHA256 variants and how to compare digests. Replace all the SHA1*() usage with the new APIs. It's a preparatory step for sha256 handling. ok stsp@

It will soon grow functions to deal with sha256 too. stsp@ agrees.

In preparation for wide sha256 support; stsp@ agrees. Change done mechanically with find . -iname \*.[cy] -exec sam {} + X ,x/<sha1\.h>/i/\n#include <sha2.h>

future fields added to the got_object_id will be implicitly zeroed instead of gibberish. ok stsp@

Allows 'got commit' to use a ".diff" suffix for temporary diff files. ok op@

Although Git itself did not care, the superfluous NUL at the end of the tag object was breaking GitHub's SSH signature detection. ok stsp@

follow the "proper secure idiom" described in the CAVEATS section of printf(3). reminded by tb@ and millert@

Found by llvm's scan-build. OK stsp

This uses the correct read and write ends of the fds returned by pipe(2) on linux. It also moves away from creating FILE* streams with fdopen and reading the stream with buf_load (which performs a fstat, and breaks due to a zero length file size on linux) by instead reading from the fd itself. Reported by abieber@, with assistance from stsp@ ok stsp@

This should fail without creating any tag. Before, ssh-keygen(1) would print an error to stderr, but got would create an unsigned tag. ok op@

This adds a new -s flag to 'got tag' that specifies the signer identity (for example, a key file) of the tagger. The tag object will include a signature that validates each of the tag object headers and the tag message. Verifying these signed tags requires maintaining an allowed signers file which maps signer identities (i.e. the email address of the tagger) to SSH public keys. See ssh-keygen(1) for more details of the allowed signers file. After creating this file and providing the path to it in got.conf(5) using the allowed_signers option, tags may be verified using with 'got tag -V tag_name'. The return code will be non-zero if a signature fails to verify. ok stsp@

ok stsp@

Saves us from doing a malloc/free call for every item on the list. ok op@

suggested by millert ok thomas_adam