Re: [PATCH/alternative/raw and rough] setup.c: denote repo wide pathspecs by ':'

Michael J Gruber <git@drmicha.warpmail.net> writes:

Just to make sure I understand that they have easy workarounds:

 - If you have a path foo/:bar, you can say

   git log master -- foo/:bar

   because ':' signals the magic and gets stripped only when it is at the
   beginning (i.e. not affecting foo/:bar); and

 - For :boz at the root level, you can say

   git log master -- '\:boz'

   because the backslash in '\:boz' makes the colon not at the beginning and
   the glob match sees '\:boz' and then matches '\:' with literal ':' at the
   beginning of the pathname ":boz".

In very old times, git used to work only from the top-level of the working tree.

The way we give an illusion that a command is restricted within the current working directory was by learning the "prefix" returned by setup_git_directory() while it chdir(2)'s up to the root level of the working tree, and then by limiting the operation to the pathspec given from the command line (each of whose elements prefixed by "prefix" by calling get_pathspec()).

Your ':'-prefix trick will naturally work very well with this arrangement. Instead of prefixing the "prefix", you would just strip ':' from the front for such a magic pathspec element, and that should be all that is necessary.

There is a small worry, though. Some codepaths have tricks that take advantage of the knowledge of the current behaviour that the resulting pathspec elements all refer to subtree under the "prefix", and try to optimize their tree traversal. I think dir.c:fill_directory()'s use of common_prefix() is safe (it recomputes what is common based on the result of get_pathspec(), not blindly using the original "prefix"), but we need to make sure there isn't a codepath that blindly believes that the original "prefix" defines the extent of the operation. Anything that understands "../" to step outside the cwd should be already safe, so I hopefully am being worried too much.

Earlier, the list consensus was that if we were to aim for uniformity, we should make everything relative to the root of the working tree when there is no pathspec by default, because you can always give a single '.' to restrict the extent of the operation to the cwd, but you cannot extend the extent of the operation without tediously counting "../". Would this ':' trick affect that argument? If a command is relative to the cwd with no pathspec, you can now give a single ':' to affect the whole tree.

As I wrote in my response to Jeff in

  http://thread.gmane.org/gmane.comp.version-control.git/133570/focus=133874

I always thought that it would be the best solution that makes the choice of the default irrelevant, and this ":" trick certainly feels like this is that solution (I also think having a good default matters).

And we can start thinking about deprecating --full-tree option, no? I like that, too ;-).