Support multiple levels of relative symlinks

Support multiple levels of relative symlinks

BUG=http://dartbug.com/15486

[ahe, 2013-12-06 08:48:06]

Once we agree on the dart2js changes, I'll update the other scripts.

[kustermann, 2013-12-06 13:50:41]

https://codereview.chromium.org/106863004/diff/1/dart/sdk/bin/dart2js
File dart/sdk/bin/dart2js (right):

https://codereview.chromium.org/106863004/diff/1/dart/sdk/bin/dart2js#newcode14
dart/sdk/bin/dart2js:14: while [ -h "$file" ]; do
I think, this doesn't work in all cases, e.g.

/home/foobar/applications/dart2js/bin -> /home/foobar/dart-sdk/bin
$ /home/foobar/applications/dart2js/bin/dart2js --version

Since dart2js itself is not a symlink, the "[ -h $file ]" will result in false.

What you need to do is to split the path into all of it's components and resolve
all of them by calling readlink until you reach the fixed point.

https://codereview.chromium.org/106863004/diff/1/dart/sdk/bin/dart2js#newcode16
dart/sdk/bin/dart2js:16: if [[ "$target" != /* ]]; then
What does this do?

https://codereview.chromium.org/106863004/diff/1/dart/sdk/bin/dart2js#newcode24
dart/sdk/bin/dart2js:24: fi
Why is that necessary?

(IMHO, a function follow_links should take a path and follow all links and
return a path without links in the components. That's it).

Additionally, the argument we pass to follow_links on line 29 is supposed to be
an absolute path, right?

[kevmoo-old, 2013-12-06 17:24:57]

DBC: don't forget the other scripts in that directory as well.