Teaching GNUFile methods to follow symlinks

[pfuntner]

On Linux systems, if File.mode is used on a file that's a symlink, it will return 0x777 because that's the mode of the symlink but mode is pretty meaningless for a symlink. By doing stat -L ... the command will automatically resolve symlinks.

I know there is the BSDFile implementation too but I don't believe I have access to a BSD system to try things out.

This addresses a problem where testinfra is used to get information on a target file but you don't want to worry about whether a symbolic link is involved - it's irrelevant. There are examples of symlinks in the Amazon Linux 2023 container:

$ docker run -it --rm amazonlinux:2023
Unable to find image 'amazonlinux:2023' locally
2023: Pulling from library/amazonlinux
1db371c0a72a: Pull complete
Digest: sha256:355f1638075375e4db3a0f7aa9cd73f79fb1a738b72035bc66a3cfda30e0053b
Status: Downloaded newer image for amazonlinux:2023
bash-5.2# ls -ld /etc/issue
lrwxrwxrwx 1 root root 16 Dec 13 00:00 /etc/issue -> ../usr/lib/issue
bash-5.2# stat /etc/issue
  File: /etc/issue -> ../usr/lib/issue
  Size: 16              Blocks: 0          IO Block: 4096   symbolic link
Device: 37h/55d Inode: 4903000     Links: 1
Access: (0777/lrwxrwxrwx)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2023-12-13 00:00:03.000000000 +0000
Modify: 2023-12-13 00:00:03.000000000 +0000
Change: 2023-12-20 11:54:00.744190148 +0000
 Birth: 2023-12-20 11:54:00.744190148 +0000
bash-5.2# stat -c %a /etc/issue
777
bash-5.2# ls -Lld /etc/issue
-rw-r--r-- 1 root root 28 Dec 13 00:00 /etc/issue
bash-5.2# stat -L /etc/issue
  File: /etc/issue
  Size: 28              Blocks: 8          IO Block: 4096   regular file
Device: 37h/55d Inode: 4904219     Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2023-12-13 00:00:03.000000000 +0000
Modify: 2023-12-13 00:00:03.000000000 +0000
Change: 2023-12-20 11:54:00.992194752 +0000
 Birth: 2023-12-20 11:54:00.992194752 +0000
bash-5.2# stat -Lc %a /etc/issue
644
bash-5.2#

I ran the tests via tox and they all passed.

This is my first pytest-testinfra pull request and I would be happy to rework it however it needs to be done.

[philpep]

Merged, thanks for this!