"brian m. carlson" <sandals@xxxxxxxxxxxxxxxxxxxx> writes: > I'm currently working on getting Git to support multiple hash algorithms > in the same binary (SHA-1 and SHA-256). In order to have a fully > functional binary, we'll need to have some way of indicating to certain > commands (such as init and show-index) that they should assume a certain > hash algorithm. > > There are basically two approaches I can take. The first is to provide > each command that needs to learn about this with its own --hash > argument. So we'd have: > > git init --hash=sha256 > git show-index --hash=sha256 <some-file > > The other alternative is that we provide a global option to git, which > is parsed by all programs, like so: > > git --hash=sha256 init > git --hash=sha256 show-index <some-file I am assuming that "show-index" above is a typo for something like "hash-object"? It is hard to answer the question without knowing what exactly does "(to) support multiple hash algorithms" mean. For example, inside today's repository, what should this command do? git --hash=sha256 cat-file commit HEAD It can work this way: - read HEAD, discover that I am on 'master' branch, read refs/heads/master to learn the object name in 40-hex, realize that it cannot be sha256 and report "corrupt ref". Or it can work this way: - read repository format, realize it is a good old sha1 repository. - do the usual thing to get to read_object() to read the commit object data for the commit at HEAD, doing all of it in sha1. - in the commit object data, locate references to other objects that use sha1 name. - replace these sha1 references with their sha256 counterparts and show the result. I am guessing that you are doing the former as a good first step, in which case, as an option that changes/affects the behaviour of git globally, I think "git --hash=sha256" would make sense, like other global options like --literal-pathspecs and --no-replace-objects. Thanks.
