>>>>> "LT" == Linus Torvalds <[EMAIL PROTECTED]> writes:
LT> Add support for a "GIT_INDEX_FILE" environment variable.
LT> We use that to specify alternative index files, which can be useful
LT> if you want to (for example) generate a temporary index file to do
LT> some specific operation that you don't want to mess with your main
LT> one with.
LT> It defaults to the regular ".git/index" if it hasn't been specified.
This is all good. I have a related issue I'd like to hear your
opinion about.
When I am not in the top-level directory, relative to the tree
structure $GIT_INDEX_FILE describes, obviously I cannot just say
"show-diff path-pattern" (or even just "show-diff") without
first chdir'ing to the top. My current workaround I use in the
jit-show-diff wrapper script is quite ugly:
- Starting from dir="${PWD-"$(pwd)"}", repeatedly do
dir=$(dirname dir) until I find a $dir/.git directory. Call
the first directory I find that has .git subdirectory
$GIT_PROJECT_TOP.
- At the same time, inspect GIT_INDEX_FILE and
SHA1_FILE_DIRECTORY environment variables. If they are not
set, set them to $GIT_PROJECT_TOP/.git/index and
$GIT_PROJECT_TOP/.git/objects, respectively and export them.
- Figure out the name of the current working directory relative
to $GIT_PROJECT_TOP. I'll call this value $R for brevity in
the following description.
- chdir to $GIT_PROJECT_TOP and run "show-diff" with the
original flags and _all_ the user supplied paths prefixed
with $R.
To illustrate what I just said:
$ /bin/ls -aF
./ ../ .git/ a/
$ /bin/ls -aF .git
. ../ HEAD index objects/
$ cd a
$ /bin/ls -aF
. ../ bar foo/
$ show-diff -r foo ; # of course this does not work.
$ jit-show-diff -r foo
The wrapper figures out that .. is the project top to chdir
to, and $R is "a/". Using these values, it eventually calls:
cd .. ; show-diff -r "a/foo"
This is not so hard to arrange in the wrapper, but this is quite
brittle. The show-diff command happens to take only -r, -z, and
-q flag parameters so the wrapper can prefix $R to all the other
paramters, but for other git core commands when to prefix $R and
when not to soon becomes a maintenance nightmare.
I am thinking about an alternative way of doing the above by
some modifications to the git core. I think the root of this
problem is that there is no equivalent to GIT_INDEX_FILE and
SHA1_FILE_DIRECTORY that tells the core git where the project
top directory (i.e. the root of the working tree that
corresponds to what $GIT_INDEX_FILE describes) is.
I am wondering if this alternative is acceptable by you before I
spend too much time on it.
- A new environment variable GIT_WORKING_TREE points at the
root of the working tree.
- Each git core command [*1*] that looks at the working tree is
modified to take the user supplied pathname as a path
relative to the current working directory, and use
GIT_WORKING_TREE value to figure out which path the user is
talking about, relative to the tree structure GIT_INDEX_FILE
describes.
There is no need for jit-show-diff-wrapper when the above change
happens. The user (or Cogito) has to set and export
GIT_WORKING_TREE once, and whereever the user happens to be the
core git command would just work as expected.
What do you think?
[Footnotes]
*1* Yes I am aware that there are tons of them that need this
surgery if we wanted to take this approach.
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