alias: expand "$@" as list of parameters quoted individually (BC) (issue4200)
Before this patch, there was no way to pass in all the positional parameters as separate words down to another command. (1) $@ (without quotes) would expand to all the parameters separated by a space. This would work fine for arguments without spaces, but arguments with spaces in them would be split up by POSIX shells into separate words. (2) '$@' (in single quotes) would expand to all the parameters within a pair of single quotes. POSIX shells would then treat the entire list of arguments as one word. (3) "$@" (in double quotes) would expand similarly to (2). With this patch, we expand "$@" (in double quotes) as all positional parameters, quoted individually with util.shellquote, and separated by spaces. Under standard field-splitting conditions, POSIX shells will tokenize each argument into exactly one word. This is a backwards-incompatible change, but the old behavior was arguably a bug: Bourne-derived shells have expanded "$@" as a tokenized list of positional parameters for a very long time. I could find this behavior specified in IEEE Std 1003.1-2001, and this probably goes back to much further before that.
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