Cannot add file COM0.c or checkout branch containing COM0.c file

[MateuszKlatecki]

• I was not able to find an open or closed issue matching what I'm seeing

Setup

• Which version of Git for Windows are you using? Is it 32-bit or 64-bit?

$ git --version --build-options

git version 2.25.0.windows.1
cpu: x86_64
built from commit: 7c71c859c97853ed057da5cbab12f3c13b5554df
sizeof-long: 4
sizeof-size_t: 8

• Which version of Windows are you running? Vista, 7, 8, 10? Is it 32-bit or 64-bit?

$ cmd.exe /c ver

Microsoft Windows [Version 10.0.18363.535]

• What options did you set as part of the installation? Or did you choose the
  defaults?

# One of the following:
> type "C:\Program Files\Git\etc\install-options.txt"
> type "C:\Program Files (x86)\Git\etc\install-options.txt"
> type "%USERPROFILE%\AppData\Local\Programs\Git\etc\install-options.txt"
$ cat /etc/install-options.txt

Editor Option: VisualStudioCode    
Custom Editor Path:                
Path Option: Cmd                   
SSH Option: OpenSSH                
Tortoise Option: false             
CURL Option: OpenSSL               
CRLF Option: CRLFCommitAsIs        
Bash Terminal Option: MinTTY       
Performance Tweaks FSCache: Enabled
Use Credential Manager: Enabled    
Enable Symlinks: Enabled           

• Any other interesting things about your environment that might be related
  to the issue you're seeing?

No

Details

• Which terminal/shell are you running Git from? e.g Bash/CMD/PowerShell/other

no matter

• What commands did you run to trigger this issue? If you can provide a
  Minimal, Complete, and Verifiable example
  this will help us understand the issue.

$ git add COM0.c
error: open("COM0.c"): No such file or directory
error: unable to index file 'COM0.c'
fatal: adding files failed

or

$ git clone https://github.com/FreeRTOS/FreeRTOS-Kernel.git
$ git checkout V10.2.1
error: invalid path 'FreeRTOS/Demo/HCS12_CodeWarrior_banked/CODE/COM0.C'
error: invalid path 'FreeRTOS/Demo/HCS12_CodeWarrior_banked/CODE/COM0.H'

• What did you expect to occur after running these commands?

I want to add file COM0.* and able to checkout branch containing that file

• What actually happened instead?

git report error

• If the problem was occurring with a specific repository, can you provide the
  URL to that repository to help us with testing?

https://github.com/FreeRTOS/FreeRTOS-Kernel.git

[dscho]

COM0 is listed as a reserved file name at https://kizu514.com/blog/forbidden-file-names-on-windows-10/, but not at https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file. The latter does talk about COM0 being a thing, though, in the "NT Namespaces" section.

So Git for Windows errs on the side of caution and interprets this as a reserved file name that cannot be used, not even with a file extension.

[MateuszKlatecki]

but it possible to create file COM0 in Windows 10 and I believe that on other Windows versions create that file is also possible

[dscho]

but it possible to create file COM0 in Windows 10 and I believe that on other Windows versions create that file is also possible

Sure, but I really want to make sure that this is not something that happens to work on your computer. That is why I erred on the side of caution. And I would really feel better if we had a link to official documentation that states that only COM1, ... COM9 are reserved, but not COM0...

[dscho]

I guess https://docs.microsoft.com/en-us/windows/win32/fileio/naming-a-file#naming-conventions is good enough.