Fix transform on exit

[Skrylar]

Prospectively fixes #381

I tried the following snippet (requires s.el) for pascal source code without the patch:

# -*- mode: snippet; require-final-newline: nil -*-
# name: procedure
# key: p
# group: control
# binding: direct-keybinding
# --
procedure ${1:DoSomething$(if yas-moving-away-p (s-upper-camel-case yas-text) yas-text)}($2);
begin
$0
end;

Casing is not adjusted correctly when leaving the $1 mirror. With this patch applied, it will correctly update the mirror. I have longer snippets where such transformed mirrors take place in more than one location, each mirror is properly updated in those cases as well. An example of such a snippet:

# -*- mode: snippet; require-final-newline: nil -*-
# name: property
# key: property
# group: types
# binding: direct-keybinding
# --
function $3 : $2;
procedure $4(${5:some-property$(if yas-moving-away-p (s-upper-camel-case yas-text) yas-text)}: $2);
property ${1:some-property$(if yas-moving-away-p (s-upper-camel-case yas-text) yas-text)} : ${2:some-type$(if yas-moving-away-p (s-upper-camel-case yas-text) yas-text)} Read ${3:get-$1$(if yas-moving-away-p (s-upper-camel-case yas-text) yas-text)} Write ${4:set-$1$(if yas-moving-away-p (s-upper-camel-case yas-text) yas-text)};

I took this patch from Google Groups, updated it to the yas- namespace and removed the inhibition of update hooks when moving between mirrors. I have been using this configuration for several weeks without incident; it may be useful for others.

https://groups.google.com/forum/#!original/smart-snippet/HEJ5JLIXhp8/DQTdvDHhOHIJ

[npostavs]

I'm planning to apply this simpler patch instead: #689.