To install Shotwell in OSX I install the first dependencies of Shotwell  successfully

brew install libGphoto2 vala libgee 


Some discussion about this issue in this thread but the accepted answer is misleading, since it is about how to install pyexiv2, not gexiv2. 

I run ./configure and get

Detected libGPhoto 2.5.x - using 2.5-aware code path.
Configured.  Type 'make' to build, 'make install' to install.


I run make and get

Package gexiv2 was not found in the pkg-config search path.
Perhaps you should add the directory containing `gexiv2.pc'
to the PKG_CONFIG_PATH environment variable
No package 'gexiv2' found
...


My .bash_profile

if [ -f ~/.bashrc ]; then
    source ~/.bashrc
fi

# http://apple.stackexchange.com/a/53058/15504
export PATH=/usr/bin:/usr/local/bin:/opt/local/sbin:$PATH


Echoing $PATH

/usr/bin:/usr/local/bin:/opt/local/sbin:/usr/local/bin:/usr/bin:/bin:/usr/sbin:/sbin:/opt/X11/bin:/usr/local/git/bin:/usr/texbin


How can you install Shotwell in OSX Yosemite? 

How can you install the dependency gexiv2 in OSX Yosemite?
As of right now there is no gexiv2 brew formula but I've created and submitted one which will hopefully get accepted soon. You can follow here: https://github.com/Homebrew/homebrew/pull/37944

Beyond that there are various dependencies of shotwell that aren't easily available through brew, for example rest and gudev which don't appear to exist anywhere for OS X. I'll have a go at creating formulas for them depending on how the first one goes.