Improving source drops documentation

[Dan Smith]

I build infrequently, but when I do, I often get errors due to out-of-date jaxp and jax-ws source bundles.  My typical process is something like this:

1) Start to build
2) Observe a failure complaining about an improper $ALT_DROPS_DIR
3) Track down my note where I wrote down the URL where I can get to a Web view of /java/devtools/...
4) Navigate to the right folder and look for file timestamps that are more recent than the last time I did this
5) Download & save the appropriate files to my source drops dir
6) Try again

I think this is more or less the "best practice," but correct me if I'm wrong.  In particular, I'm not relying on mounted access to the /java filesystem, as I think most veteran Sun employees do, and I'm not using ALLOW_DOWNLOADS, which is discouraged in the build documentation.

Short of getting rid of the source drops entirely, it seems like there's a lot that could be done to streamline this process.

- It would be nice if the sanity check caught the missing files, rather than waiting to complain in the middle of the build.  (Fortunately, at least these get built early.)

- The error message would be a lot more useful if it told me the name(s) of the missing file(s) (which includes the version number) rather than assuming that my ALT_DROPS_DIR setting is wrong.

- Even better, the error message could spit out the URL(s) where I could download the file(s)!  (This should be the same URL as used by ALLOW_DOWNLOADS.)

- The docs ("Creation of New Source Drop Bundles") say the OpenJDK team puts new bundles in "/java/devtools/...", which is difficult to access.  (Can non-Oracle folks get to it? I rely on the javaweb internal server, which happened to be down today...)  Is/could this directory be made available somewhere public, too?

Thanks,
Dan