Just a quick note about the macOS install instructions 
(https://tcp.rip/text/misc/install-castor.txt.html)

> # 3. Install dependencies with homebrew
> 
> brew install gdk-pixbuf
> brew install atk
> brew install pango
> brew install gtk+3
> 
> #   (possibly installing just gtk+3 installs all the
> #   others.. i did it in a silly order)

Installing gtk+3 does indeed install the others. This should be

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+I'm about to try git send-email!
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2.25.0
[message trimmed]

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+I'm about to try git send-email!
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2.25.0
[message trimmed]

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+I have successfully used git send-email!
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2.22.0
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+I'm about to try git send-email!
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2.22.0
[message trimmed]

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+Wooooo I'm trying git send-email!
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2.22.0
[message trimmed]