Reported by Matthias Schmidt ok tb@

When trying to open a worktree from a list of metadata directories (.got, .cvg), error out when a worktree is found but is already locked. Skipping it and proceeding would result in a confusing "no git repository found" error from tog and gotadmin. ok stsp

This prevents mixing the use of got and cvg clients in the same work tree. Avoids confusion going forward while cvg differentiates itself further. tog(1) and gotadmin(1) remain compatible with both work tree formats. These tools only read work trees to locate the corresponding repository.

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>

thanks for all the help massaging this diff

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

suggested by millert ok thomas_adam

Move a small amount of code from worktree.c to a new file worktree_open.c, which contains everything required to open and close a work tree and inspect some of its basic parameters. This can be used by gotadmin. ok tracey