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I talked with a friend and I realized I'm not explaining this very well. Let me try again.
The reason --format-executable should default to on is because the binaries created by "gem" have the name of the "ruby" tied to that version of "gem".
Here's two uses cases in full:
----use case 1-----------------------
I install ruby 1.8.
I use "./configure" when compiling it.
The binaries are in /usr/bin/ and do not have a suffix.
I decide I want to work on ruby 1.9.1 as well.
I use "./configure --program-suffix=19" when compiling it.
The binaries are also in /usr/bin but all end with "19", such as "/usr/bin/ruby19".
Lets say I ZenTest for 1.8:
$ gem install ZenTest
This creates /usr/bin/autotest. This executable is intimately tied to ruby 1.8; it begins with "#!/usr/bin/ruby -ws" -- it cannot be used for ruby 1.9 (yet) because the libraries are not installed in ruby 1.9 and the executable it points to is the 1.8 executable.
Now lets say I want to install autotest for ruby 1.9:
$ gem19 install ZenTest
By default, no new binaries are created since they already exists.
The executable /usr/bin/autotest is still tied to ruby 1.8.
This causes confusion by the user; they just installed autotest for ruby 1.9 but it still is running ruby 1.8.¶
----use case 2-----------------------
My system administrator installs ruby 1.8 using "./configure" with no arguments.
My system administrator installs ruby 1.9.1 using "./configure --program-suffix=19"
I (a non-system-administrator) wants to install ZenTest for both:
$ gem install ZenTest
[output showing it is installed to ~/.gem]
$ gem19 install ZenTest
[output showing it is installed to ~/.gem]
So now I have two "autotest" binaries:
~/.gem/ruby/1.8/bin/autotest
and
~/.gem/ruby/1.9.1/bin/autotest
If my PATH includes both, then which "autotest" I get depends on my PATH order. The only way I can distinguish between the two executables is by changing my PATH on the fly. Not very useful if I want to be able to easily switch between both versions to verify it works in both versions of Ruby.¶
I think that without --format-executable as a default, this is too confusing for a normal user.
I agree that a --no-format-executable option should be kept around, though. Choice is good.
Ciao!
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