help: spelling fixes

help: attempt to clarify that pager usage is not output length based This may be too subtle of a change to get the point across, but when I first read the original text, I thought maybe the pager would only be invoked if writing more than a screenful. The distinction between this and a pager that simply exits after printing less than a screenful is important on Windows, given the inability of `more` to color output.

help: document color/pager pitfalls on Windows Even though I figured this out a few weeks ago, I was initially puzzled where the color went when I upgraded to 4.2 on a different Windows machine. Let's point users reading the help into the right direction. I wonder if we should be even more explicit about cmd.exe/MSYS/pager/color interplay, but at least all of the breadcrumbs are here (I think).

webcommands: use fctx.isbinary

annotate: use fctx.isbinary

fileset: use fctx.isbinary instead of util.binary(fctx.data()) filectx provides "isbinary" to test if the data is binary. Let's use it. This enables other filectx implementations (like LFS) to override the isbinary test.

internals: document that "branches" is a legacy wire command Modern clients use a different discovery mechanism.