clone: create intermediate directories of destination repo
The shell version used to use "mkdir -p" to create the repo path, but the C version just calls "mkdir". Let's replicate the old behavior. We have to create the git and worktree leading dirs separately; while most of the time, the worktree dir contains the git dir (as .git), the user can override this using GIT_WORK_TREE.
We can reuse safe_create_leading_directories, but we need to make a copy of our const buffer to do so. Since merge-recursive uses the same pattern, we can factor this out into a global function. This has two other cleanup advantages for merge-recursive:
1. mkdir_p wasn't a very good name. "mkdir -p foo/bar" actually creates bar, but this function just creates the leading directories.
2. mkdir_p took a mode argument, but it was completely ignored.
Acked-by: Daniel Barkalow <email@example.com> Signed-off-by: Junio C Hamano <firstname.lastname@example.org>