There was a 'command -v' check back when this script landed in
aa748b62 (makefile stuff, 2016-09-19, #30), but it was removed in
741873ad (Makefile: suggests install.tools, 2016-09-28, #70). The
default changed from 'gometalinter' to '${GOPATH}/bin/gometalinter' in
6c9628cd (Build and install from GOPATH, 2017-01-17, #320) and the -f
guard landed in 9c240aed (lint: Exit and give instructions when linter
missing, 2017-09-06, #850). This commit brings us back to our
original 'command -v' check (in POSIX [1]), which allows support for
both filesystem and $PATH based commands (and shell aliases, etc.).
I've also made the default LINTER more flexible, using the
${parameter:-word} syntax from POSIX [2]. That keeps the default
linter unchanged, but allows callers to set the LINTER environent
variable to override. For example:
$ LINTER=gometalinter .tool/lint
will use the linter from your $PATH.
[1]: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/command.html
[2]: http://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_06_02
Signed-off-by: W. Trevor King <wking@tremily.us>
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