Strip the GIT_EXEC_PATH Makefile parameter. Replaced it by the more Unixy

``prefix''. There is no need to install git-flow inside git's libexec dir by
default. It just needs to be *somewhere* on the PATH.

Makefile

-AUTO_DETECTED_GIT_EXEC_PATH := $(shell git --exec-path 2>/dev/null || echo /usr/libexec/git-core)
-GIT_EXEC_PATH=$(AUTO_DETECTED_GIT_EXEC_PATH)
+prefix=/usr/local
 
 # files that need mode 755
 EXEC_FILES=git-flow
@@ -20,11 +19,11 @@ all:
 
 install:
 	@test -f gitflow-shFlags || (echo "Run 'git submodule init && git submodule update' first." ; exit 1 )
-	install -d -m 0755 $(GIT_EXEC_PATH)
-	install -m 0755 $(EXEC_FILES) $(GIT_EXEC_PATH)
-	install -m 0644 $(SCRIPT_FILES) $(GIT_EXEC_PATH)
+	install -d -m 0755 $(prefix)/bin
+	install -m 0755 $(EXEC_FILES) $(prefix)/bin
+	install -m 0644 $(SCRIPT_FILES) $(prefix)/bin
 
 uninstall:
-	test -d $(GIT_EXEC_PATH) && \
-	cd $(GIT_EXEC_PATH) && \
+	test -d $(prefix)/bin && \
+	cd $(prefix)/bin && \
 	rm -f $(EXEC_FILES) $(SCRIPT_FILES)

README.mdown

@@ -21,15 +21,10 @@ Then, you can install `git-flow`, using:
 
 	$ sudo make install
 
-By default, this will look for the directory where Git is already installed,
-and install the git-flow extension alongside the other Git subcommands. If git
-is not on the system's `PATH`, it tries `/usr/libexec/git-core`. To explicitly
-override this setting in case you have installed Git in another location, use:
+By default, git-flow will be installed in /usr/local. To change the prefix
+where git-flow will be installed, simply specify it explicitly, using:
 
-	$ sudo make GIT_EXEC_PATH=/your/custom/path install
-
-You rarely need to override this manually, the default 'make install' should do
-fine.
+	$ sudo make prefix=/opt/local install
 
 Or simply point your `PATH` environment variable to your git-flow checkout
 directory.