Support relative path for snippet's filename attribute

[csessh]

closes #320

This pull request contains changes to support both relative and absolute path types for snippet file's filename attribute.

Given the test case listed in #320:

The same case presented in the issue

Given this config:

[General]
...
SnippetDirs = []
SnippetFile = "~/.config/test/test.toml"
...

SnippetFile is a relative path which expands to /home/csessh/.config/test/test.toml

Current Pet version:

fw13 :: ~/Documents/pet ‹feat-syspath*› » pet new 
Command> ping google.com
Description> hey Google
fw13 :: ~/Documents/pet ‹feat-syspath*› » cat ~/.config/test/test.toml 
   1   │ 
   2   │ [[Snippets]]
   3   │   Description = "hey Google"
   4   │   Filename = "/home/csessh/.config/test/test.toml"
   5   │   Output = ""
   6   │   Tag = []
   7   │   command = "ping google.com"

As expected, ~/.config/test/test.toml expands to /home/csessh/.config/test/test.toml

Using feature branch version:

fw13 :: ~/Documents/pet ‹feat-syspath*› » go run main.go new      
Command> ping google.com
Description> Hey Goolge
fw13 :: ~/Documents/pet ‹feat-syspath*› » go run main.go edit
fw13 :: ~/Documents/pet ‹feat-syspath*› » cat ~/.config/test/test.toml
   1   │ 
   2   │ [[Snippets]]
   3   │   Description = "Hey Goolge"
   4   │   Filename = "~/.config/test/test.toml"
   5   │   Output = ""
   6   │   Tag = []
   7   │   command = "ping google.com"

file path stays the same. The same result applies for the following test case:

[General]
...
SnippetDirs = []
SnippetFile = "/home/csessh/.config/test/test.toml"
...

Full path is rendered for every snippets.

I didn't go too deep into testing filename with the use of multiple directories as I ran into #321 problem. However, I did include the safeguard check for it in this PR too.

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[csessh]

@RamiAwar could you review this PR, please?

[RamiAwar]

How are you handling interaction with snippet directories?

[csessh]

Directories can also be expressed in relative path format, e.g. ~/.config/pet/.
This PR doesn't touch this feature's logic, apart from expanding paths to ensure snippet files can be read/opened.

[csessh]

Resolved conflicts

[RamiAwar]

Awesome, thank you! @csessh Will review this carefully this week. Thanks for waiting 🙏🏼 ✨

[RamiAwar]

Why is this necessary?

[csessh]

If I recall correctly, that's because it would lead to new snippet filename being incorrect.

pet/snippet/snippet.go

Line 94 in adfb69a

snippetFile = config.Conf.General.SnippetDirs[0] + fmt.Sprintf("%s.toml", strings.ToLower(sanitize.BaseName(snippet.Description)))

for example:

/var/tmp/petNewCommand.toml

instead of

/var/tmp/pet/NewCommand.toml