piholeDebug: Diagnose output if (Web) git directory is not found

[ganto]

By submitting this pull request, I confirm the following:

• I have read and understood the contributors guide, as well as this entire template.
• I have made only one major change in my proposed changes.
• I have commented my proposed changes within the code.
• I have tested my proposed changes, and have included unit tests where possible.
• I am willing to help maintain this change if there are issues with it later.
• I give this submission freely and claim no ownership.
• It is compatible with the EUPL 1.2 license
• I have squashed any insignificant commits. (git rebase)

---

What does this PR aim to accomplish?:
If Pi-hole was installed without Web interface the piholeDebug.sh currently omits any output in the version check for the "Web" component:

*** [ DIAGNOSING ]: Core version                                                                                                                                                                                                                                                                                              
[i] Core: v5.2.1 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249) 
[i] Remotes: origin     https://github.com/pi-hole/pi-hole.git (fetch)                                                                                         
             origin     https://github.com/pi-hole/pi-hole.git (push)                                                                                          
[i] Branch: master                                                                                                                                                                                                                                                                                                            
[i] Commit: v5.2.1-0-g0d8ece1                                                                                                                                  
                                                                                                                                                               
*** [ DIAGNOSING ]: Web version                                                                                                                                                                                                                                                                                               
                                                                                                                                                                                                                                                                                                                              
*** [ DIAGNOSING ]: FTL version                                                                                                                                
[✓] FTL: v5.3.2 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)

I guess it would be helpful to have more details what's up with the "Web" component.

How does this PR accomplish the above?:
I adjusted the code to print a note when the "Web" component has been disabled on purpose:

*** [ DIAGNOSING ]: Core version
[i] Core: v5.2.1 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)
[i] Remotes: origin     https://github.com/pi-hole/pi-hole.git (fetch)
             origin     https://github.com/pi-hole/pi-hole.git (push)
[i] Branch: master                           
[i] Commit: v5.2.1-0-g0d8ece1             

*** [ DIAGNOSING ]: Web version 
[i] Web: Disabled in setupVars.conf via INSTALL_WEB_INTERFACE=false           
                                                                               
*** [ DIAGNOSING ]: FTL version                                      
[✓] FTL: v5.3.2 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)

And I also added a proper error message if the git directory is not found. This works for all the components tested in compare_local_version_to_git_version(). Here an example output if INSTALL_WEB_INTERFACE=true (or missing) in the setupVars.conf:

*** [ DIAGNOSING ]: Core version
[i] Core: v5.2.1 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)
[i] Remotes: origin     https://github.com/pi-hole/pi-hole.git (fetch)
             origin     https://github.com/pi-hole/pi-hole.git (push)
[i] Branch: master
[i] Commit: v5.2.1-0-g0d8ece1

*** [ DIAGNOSING ]: Web version
Directory /var/www/html/admin doesn't exist

*** [ DIAGNOSING ]: FTL version
[✓] FTL: v5.3.2 (https://discourse.pi-hole.net/t/how-do-i-update-pi-hole/249)

What documentation changes (if any) are needed to support this PR?:
No changes needed.

[pralor-bot]

This pull request has been mentioned on Pi-hole Userspace. There might be relevant details there:

https://discourse.pi-hole.net/t/pi-hole-core-web-v5-2-2-and-ftl-v5-3-3-released/41998/1