bugfix: bin/make: need to leave bin/, ~/bin/ in the PATH when running make nonrecursively, so that commands invoked by it which are located in these dirs (e.g. put, which will be used by `make inputs/upload`) can still be found. this requires using command()'s new nonrecursive=1 flag instead of running no_PATH_recursion, so that no_PATH_recursion() only affects the resolution of the command path, but does not propagate the filtered PATH to the invoked command itself.

lib/sh/util.sh: command(): added nonrecursive=1 flag, which uses cmd2abs_path to run an external command nonrecursively

lib/sh/util.sh: added cmd2abs_path, which makes the command in $1 nonrecursive

bugfix: lib/sh/util.sh: PATH_rm(): also need to remove adjacent occurrences of the same path (or occurrences which become adjacent when other paths are removed), which :...: matching wasn't doing because the trailing : is consumed, preventing it from being matched at the beginning of the next path. since unlike filesystem paths with /, it is not necessary for a match to span multiple :-separated sections, we can just use new split() to split apart the PATH into an array of paths, filter each path, and join() them back together.

lib/sh/util.sh: added split()

lib/sh/util.sh: auto-echo common external commands: added `which`

lib/sh/util.sh: auto-echo common external commands: use simpler echo_run instead of command since logging handling is not needed

added backups/vegbien.r9897.backup.md5

lib/sh/sync.sh: upload(): documented that each --include path is relative to the currdir, not the root dir of the upload ($local_dir). this feature, although previously unintended, is actually better because the user can change to a subdir of the root dir and specify upload paths relative to the dir they are in. however, when invoking upload() from a script with --include paths specified, this means you need to use an absolute path (e.g. "$(dirname "${BASH_SOURCE⁰}")"/...; or the value that will become $local_dir, which for sync_upload() is $root_dir).

backups/.rsync_ignore: replaced with .rsync_filter.upload to allow uploading new backups but not deleting existing backups if they don't exist on the local (rsync-invoking) side; and .rsync_filter.download to avoid downloading backups to the local side. this allows storing older backups just on jupiter, where there is much more disk space. note that this change must be made on the remote side (jupiter) for it to be effective, because these are remote-side rules and are only processed by the remote-side rsync instance.