previously committed file untracked prevent checking out an old tag/branch

Hi,

I had this situation:

we used to have a properties file in our project that was used by ant
to build it.
That file was tracked since the beginning of the project (several months ago).

let's call it:
build.properties

(the project is on SVN and I'm the only one to use git)

Since everyone in the project has different directories paths I
decided to untrack the file
create a new template file and track it instead:

so I did something like this:

cp build.properties build.properties.template
vim build.properties.template
echo build.properties >> .git/info/exclude
git rm --cached build.properties
git add build.properties.template
git commit -m "finally we don't overwrite it each other anymore"

Now I had to switch back to a tag that still have that file
(build.properties) tracked to fix some
issue there but when I try I get:

error: Untracked working tree file 'build.properties' would be
overwritten by merge.

How would you handle a situation like this?

I only can think of doing a backup of my build.properties, delete it
and check out the tag or I just delete it and rebuild
it from the template later.

I did it but that made me think on it.

Actually what I really wanted here was the possibility to "locally
track" that file...

something like
git local <file>

that will have that file indexed by git so I can switch to branch that
have that file without loosing it when I go back.
furthermore that would allow me to keep versions of my local file even
if I don't want to commit it.
I could see if I accidentally modified it.

This could be useful, in my opinion.

Is there on git a feature to do something like that?
Do you think it could be useful or do you see any possible problem about that?

Regards,
Daniele