Always resolve relative include paths relative to the including Taskfile

[theunrepentantgeek]

Enforces consistency by always resolving relative filepath references to Taskfiles from the directory containing the parent Taskfile.

Resolves #822

Previously, relative filepath references were resolved multiple times, leading to some unanticipated behaviour.

To illustrate, consider the following directory structure:

• /path/to/project/Taskfile.yaml # top level
• /path/to/project/alpha/Taskfile.yaml # first subfolder
• /path/to/project/common/Taskfile.yaml # second subfolder, a sibling of alpha

With the following includes

# /path/to/project/Taskfile.yaml
includes:
  alpha:
    taskfile: ./alpha/Taskfile.yaml
    dir: ./alpha
  common: 
    taskfile: ./common/Taskfile.yaml
    dir: ./common

# /path/to/project/alpha/Taskfile.yaml
includes:
  common: 
    taskfile: ../common/Taskfile.yaml
    dir: ../common

When loading /path/to/project/alpha/Taskfile.yaml, the include ../common/Taskfile.yaml is correctly being resolved as /path/to/project/common/Taskfile.yaml.

But when loading the top level Taskfile /path/to/project/Taskfile.yaml, that same import (../common/Taskfile.yaml) is being resolved a second time, as /path/to/common/Taskfile.yaml, leading to an error.

This fix modifies all includes to use absolute paths, ensuring the correct Taskfile is read.

[theunrepentantgeek]

Pulling back to draft status while I fix the failing tests.

[theunrepentantgeek]

This diff makes it look as though execext.Expand() has been removed - it's still present, just lower down on line #95.

[theunrepentantgeek]

I think this is now ready for review.

One note. Instead of doing something "clever" to ensure error messages retained their use of relative paths, I opted to update the tests to reflect the fully-qualified paths that now show up. Keeping things simple seemed the smarter option.

[andreynering]

Hi @theunrepentantgeek, thanks a lot for your contribution!

I merged this with a few changes at e396f4d.

I added a test and changed Expand to to run before converting the path to absolute. (Expand is there to make include paths like ~/taskfiles, i.e. the user home directory, work).