Re: [PATCH] bash-completion: Print a useful error when called in a non-bash shell

Andrew Sayers [off-list ref] writes:

Detect whether the shell supports process substitution with <()
Shells that fail the test will not be able to load git-completion.bash

If a bad shell is found, print a warning which gives the user as much debugging
information as possible.

This was added in response to a bug report on the git mailing list:
  http://permalink.gmane.org/gmane.comp.version-control.git/151723

Signed-off-by: Andrew Sayers <redacted>
---

+# Check in case we were called with something like "sh git-completion.bash":
+$(
+	exec 2>/dev/null
+	$(exec < <( ))
+ )
+if [[ 0 -ne $? ]]
+then
+	cat <<EOF
+
+ERROR: you don't seem to be running a full bash shell.
+git-completion.bash is probably about to fail with a syntax error.
+If you are sure that your system is calling git-completion.bash from a bash,
+then please include the following in a bug report to git@vger.kernel.org:

I needed to read this twice to realize that majority of people who will
ever see this message on their screen are _not_ expected to send any bug
report to us.  Also if the user's "full bash" groks <() indirection but
still fails to run completion script correctly, this message does not help
them to find where to file a bug report at all.

I do agree that there need to be a way to find that information for the
end users, especially for those who just use binary-packaged git given by
their distros, but this codepath is _not_ the place to do it.

How about replacing these with something simple like:

    echo >&2 "You are not running full 'bash'; exiting." ; exit 127

+	BASH_VERSION: {$BASH_VERSION}
+	BASHOPTS: {$BASHOPTS}
+	SHELLOPTS: {$SHELLOPTS}
+	POSIXLY_CORRECT: {$POSIXLY_CORRECT}
+EOF
+	echo -n "	command line: {"
+	tr '\0' ' ' < /proc/$$/cmdline

This looks like a Linux-ism to me.