What do you mean by "my editor"? And what do you mean by "git -w"? Are you using an editor and command line tools instead of an IDE? May I recommend IntelliJ IDEA? It is the best java IDE ever, and it has no problem with either kind of whitespace, or even with mixed whitespace within the same file.
Generally, if a massive change has to be made to the code base, like changing the formatting, it should be done all at once and as early as possible.
If you don't do that, then files will keep being committed in the future for no reason other than whitespace changes, unnecessarily bloating the history lists, and forcing you to often request diffs of files only to be told "files differ only in whitespace".
Also, it will never be obvious whether a file was committed due to actual changes or only due to whitespace changes, so if two or more developers happen to have different whitespace and/or formatting settings by mistake, it will take you some time and several commits where one developer is undoing the whitespace changes of another until you realize that this discrepancy exists.
By reformatting and committing everything at once, the revision number of that commit (which will from that day on be known as "The Great Big Reformatting") will be memorized by everyone, so whenever you see that revision number you will know to not even request a diff.
Plus, from that moment on, everyone will know that subsequent commits due to whitespace changes only should not be made, because they are obviously the result of a configuration mismatch between developers.
Now, on the question of whether you should convert the entire code base to conform to a particular coding style, this is not an easy thing to answer without knowing the particulars of your situation. The obvious answer, which anyone out there will tell you, is that a consistent coding style is important, and that even a bad (by whatever standard) but consistent style is better than an inconsistent style. However, there are some practical questions to be asked first:
Do most of the important contributors at your workplace agree?
Are there any contributors who, despite being a minority, might rage-quit if you proceed with this? And how important are they?
How big of a variety of styles do you have? Is it only tabs vs. spaces, or does it include other major aspects of coding style like Allman vs. Egyptian braces? People should be flexible enough to not mind a small variety.
But mostly: Is it really necessary?
I mean, in my current job, each developer is working on a specific, clearly delineated subset of the code base, so I don't delve (much) into other people's code, and nobody delves into my code, so it does not really matter that we have vastly different styles. It neither picks my pocket nor breaks my leg that a colleague wraps his lines at column 80. (Ssssh, he probably does not know how to change the relevant setting.) The situation would be quite different if we had developers whose job involved frequently dealing with other people's code. If you do have such a situation, and if the coding styles vary so much as to make it hard for them to do their job, then you probably should enforce a single coding style for everyone. Otherwise, perhaps not.
One more final note:
In theory, it should be possible to resolve this issue with technical means so that a) different developers can work on the same code, and yet b) each developer gets to enjoy whatever coding style he or she prefers. The way this would (in theory) be accomplished would be by having code formatted to your preferred style when updating from the version control system, and re-formatted to the "project style" right before committing. Unfortunately, as of today, there are no tools that will do this as far as I know. IntelliJ IDEA gets close by supporting multiple styles, including a "personal style" and a "project style", but it is not fully automated: you still get to browse unmodified code in "project style", if you re-format any files to your "personal style" they will unfortunately appear as modified with respect to the pristine copies, (which is probably a shortcoming of the version control system and not of IDEA,) and the (optional of course) step which re-formats files back to "project style" when committing leaves all of your local copies in "project style" again. If anyone knows of anything that achieves more than that, please do say.