Re: [PATCH 4/4] Clean up work-tree handling

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From: Junio C Hamano
Date: Tuesday, July 31, 2007 - 10:17 pm

Johannes Schindelin <Johannes.Schindelin@gmx.de> writes:


Without continuing with negatives, let's try to define the new,
corrected world order.

I do not think the following is exactly what your cleaned-up
version tries to perform, but I am writing this down primarily
to demonstrate the style and the level of detail I expect to
accompany a clean-up patch like this.

----------------------------------------------------------------

Definitions:

 - You can have "checked out" files on the filesystem, and such
   files are said to be in your "work tree".  The directory
   on the filesystem that corresponds to the toplevel entries of
   the index and the tree objects directly contained in the
   commit objects is called "the toplevel of the work tree",
   or simply "work tree" if it is not ambiguous from the
   context.

 - The directory that holds git repository information is called
   "git directory".  This is typically .git directory at the
   toplevel of your work tree, but not necessarily so.

 - You can perform many git operations without a work tree, but
   some operations fundamentally require you to have one
   (e.g. checkout and diff, unless two tree-ishes are given, do
   not make sense without a work tree).

There are four predicates, two interrogators, and two
manipulators:

 - is_inside_git_dir(): this returns true if the $cwd is the git
   directory or its subdirectory. [IS THIS STILL NEEDED???]

 - is_inside_work_tree(): this returns true if the $cwd is
   inside work tree (i.e. either at the toplevel of the work
   tree or its subdirectory).  [NEEDSHELP: is .git in the usual
   layout considered "is_inside_work_tree()"?  Should it?]

 - is_bare_repository(): this returns true if no work tree is
   found.  There is a corresponding function usable from the
   scripts.

 - require_work_tree (shell): this is called by scripts that
   needs to have a work tree to operate, and barfs otherwise.

 - get_git_dir(): this returns the location of the git
   directory.  With GIT_DIR environment variable, or --git-dir
   command line option, you can tell git to use a specific
   directory as the git directory.  Otherwise a directory that
   looks like a git directory and whose name is .git is looked
   for, in the $cwd or its parent directory.  If there is no
   such directory, and if the $cwd looks like a git directory,
   $cwd is the git directory.

 - get_git_work_tree(): this returns the location of the work
   tree; it returns NULL if there is none.  The command line
   option --work-tree, or the environment variable GIT_WORK_TREE
   can specify the location; otherwise, git directory is looked
   for so that its configuration file can be read.  If
   core.worktree is there, that specifies the location.
   Otherwise, if the basename of the git directory is .git, it
   is the parent directory of the git directory.  Otherwise, you
   do not have work tree.

 - set_git_dir(): used to set the git directory, internally to
   handle --git-dir option;

 - set_work_tree(): used to set the git directory, internally to
   handle --work-tree option;

----------------------------------------------------------------

After writing the above down, it strikes me odd that we do not
have a predicate that says "we know the work tree is there".

If a command wants a work tree, and if you are outside the work
tree, then is_inside_work_tree() returns false and
get_git_work_tree() returns non NULL, so that is a good pair of
interface that can be mixed and matched (e.g. you can chdir to
the former to perform the whole tree operation, or refuse to
perform, based on is_inside_work_tree being false, cwd relative
operations).


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Messages in current thread:
[PATCH 0/9] work-tree clean ups, Johannes Schindelin, (Sun Jul 29, 4:23 pm)
[PATCH 1/9] Add is_absolute_path() and make_absolute_path(), Johannes Schindelin, (Sun Jul 29, 4:24 pm)
[PATCH 2/9] Add functions get_relative_cwd() and is_inside ..., Johannes Schindelin, (Sun Jul 29, 4:24 pm)
[PATCH 3/9] white space fixes in setup.c, Johannes Schindelin, (Sun Jul 29, 4:24 pm)
[PATCH 4/9] Clean up work-tree handling, Johannes Schindelin, (Sun Jul 29, 4:25 pm)
[PATCH 5/9] Add set_git_dir() function, Johannes Schindelin, (Sun Jul 29, 4:25 pm)
[PATCH 6/9] work-trees are allowed inside a git-dir, Johannes Schindelin, (Sun Jul 29, 4:25 pm)
[PATCH 7/9] init: use get_git_work_tree() instead of rolli ..., Johannes Schindelin, (Sun Jul 29, 4:25 pm)
[PATCH 8/9] Fix t1501 for updated work-tree logic, Johannes Schindelin, (Sun Jul 29, 4:26 pm)
[PATCH 9/9] Fix t1500 for sane work-tree behavior, Johannes Schindelin, (Sun Jul 29, 4:26 pm)
[UNWANTED PATCH] Die if core.bare = true and core.worktree ..., Johannes Schindelin, (Sun Jul 29, 4:29 pm)
Re: [PATCH 0/9] work-tree clean ups, Johannes Schindelin, (Tue Jul 31, 5:28 pm)
[PATCH 1/4] Add is_absolute_path() and make_absolute_path(), Johannes Schindelin, (Tue Jul 31, 5:28 pm)
[PATCH 2/4] Add functions get_relative_cwd() and is_inside ..., Johannes Schindelin, (Tue Jul 31, 5:29 pm)
[PATCH 3/4] Add set_git_dir() function, Johannes Schindelin, (Tue Jul 31, 5:29 pm)
[PATCH 4/4] Clean up work-tree handling, Johannes Schindelin, (Tue Jul 31, 5:30 pm)
Re: [PATCH 0/9] work-tree clean ups, Junio C Hamano, (Tue Jul 31, 5:55 pm)
Re: [PATCH 0/9] work-tree clean ups, Johannes Schindelin, (Tue Jul 31, 6:13 pm)
Re: [PATCH 4/4] Clean up work-tree handling, Junio C Hamano, (Tue Jul 31, 10:17 pm)
Re: [PATCH 4/4] Clean up work-tree handling, Junio C Hamano, (Wed Aug 1, 1:59 am)
Re: [PATCH 0/9] work-tree clean ups, Johannes Schindelin, (Wed Aug 1, 3:56 am)
Re: [PATCH 2/4] Add functions get_relative_cwd() and is_in ..., Johannes Schindelin, (Wed Aug 1, 4:38 am)
Re: [PATCH 4/4] Clean up work-tree handling, Johannes Schindelin, (Wed Aug 1, 4:46 am)
Re: [PATCH 4/4] Clean up work-tree handling, Johannes Schindelin, (Wed Aug 1, 4:53 am)
[NOT-SERIOUS PATCH] Make get_relative_cwd() not accept NUL ..., Johannes Schindelin, (Wed Aug 1, 8:26 am)
[PATCH] get_relative_cwd(): clarify why it handles dir == NULL, Johannes Schindelin, (Wed Aug 1, 11:26 am)
Re: [PATCH 4/4] Clean up work-tree handling, Junio C Hamano, (Thu Aug 2, 12:04 am)