Just add the following line to your ~/.vimrc
:
set tags=./tags;,tags;
It means "look for a tags
file in the directory of the current file, then upward until /
and in the working directory, then upward until /
".
In other words, no matter where you are in your project, Vim will pick up the right tags
for the project.
:help tags
is a good read, it would have saved you the hassle of posting a question here.
Note: the magic part of that line is the ;
of "upward search". You can give Vim an upper limit like this: ;$HOME
.