File.open("|/usr/bin/co ...") does not seem to work in Ruby 2.7

[arpepper]

Sorry, I am not super familiar with git, and am even less familiar with
Ruby. But when upgrading from Ubuntu 18.04 to Ubuntu 20.04 Ruby
(going from 2.5 to 2.7) seemed to change enough
to break rcs-fast-export.rb

Making the following change seemed to work.

Adrian.

arpepper@u2004cvs2git:~/git/rcs-fast-export$ git diff
diff --git a/rcs-fast-export.rb b/rcs-fast-export.rb
index 4128335..62246a2 100755
--- a/rcs-fast-export.rb
+++ b/rcs-fast-export.rb
@@ -381,7 +381,8 @@ module RCS
        # TODO: what if a revision does not end with newline?
        # TODO this should be done internally, not piping out to RCS
        def RCS.expand_keywords(rcsfile, revision)
-               ret = ::File.read("|co -q -p#{revision} #{Shellwords.escape rcsfile}")
+               # ret = ::File.read("|/usr/bin/co -q -p#{revision} #{Shellwords.escape rcsfile}")
+               ret = ::IO.popen("/usr/bin/co -q -p#{revision} #{Shellwords.escape rcsfile}")
                lines = []
                ret.each_line do |line|
                        lines << line
arpepper@u2004cvs2git:~/git/rcs-fast-export$ 

[arpepper]

Sorry, the markdown initally obfuscated my intended text comment. Eventually I deduced and remembered <pre>.

But this simple description of the change might still help.

Essentially, replace the line...
ret = ::File.read("|co -q -p#{revision} #{Shellwords.escape rcsfile}")

With...
ret = ::IO.popen("/usr/bin/co -q -p#{revision} #{Shellwords.escape rcsfile}")

[arpepper]

I should have mentioned that the code only causes a problem if you specify "--expand-keywords" on your command line. So a work-around is to not use that option. (And users who do not use the option will not encounter the problem).