Use git "log" command in another folder

I have some php files in a Folder A (which is a git project). In these php file I want to execute "git log" but for the folder B. Folder B is another git project (so log is different between A and B).

How I can do that with shell command ?

From, man git:

You can do this with the --git-dir parameter, before passing any commands.

git --git-dir /foo/bar/.git log

(Specifying the .git directory is necessary.) From the documentation:

--git-dir=<path>

Set the path to the repository. This can also be controlled by setting the GIT_DIR environment variable. It can be an absolute path or relative path to current working directory.

With git 1.8.5 (Q4 2013), you will have another choice, instead of setting --git-dir.
If you want to execute git log in folder B, type:

git -C B log

Just like "make -C <directory>", "git -C <directory> ..." tells Git to go there before doing anything else.

See commit 44e1e4 by Nazri Ramliy:

It takes more keypresses to invoke git command in a different directory without leaving the current directory:

1. (cd ~/foo && git status)
git --git-dir=~/foo/.git --work-tree=~/foo status
GIT_DIR=~/foo/.git GIT_WORK_TREE=~/foo git status
2. (cd ../..; git grep foo)
3. for d in d1 d2 d3; do (cd $d && git svn rebase); done

The methods shown above are acceptable for scripting but are too cumbersome for quick command line invocations.

With this new option, the above can be done with fewer keystrokes:

1. git -C ~/foo status
2. git -C ../.. grep foo
3. for d in d1 d2 d3; do git -C $d svn rebase; done