fstab: Allow consecutive commas in mount options

[crobinso]

Fix the fstab lens to handle consecutive commas in mount options (e.g., "rw,,nodev"). This has been seen in the wild via libguestfs/ virt-v2v:

https://issues.redhat.com/browse/RHEL-77279

The fix changes the comma separator from matching a single comma to matching one or more consecutive commas.

🤖 Generated with Claude Code

[rwmjones]

This works for me. However it doesn't parse:

/dev/mapper/vg00-vartmp /var/tmp xfs rw,nodev,nosuid,noexec,relatime,, 0 0

saying:

/home/rjones/d/augeas/lenses/tests/test_fstab.aug:187.2-199.3:exception thrown in test
/home/rjones/d/augeas/lenses/tests/test_fstab.aug:187.7-.99:exception: Iterated lens matched less than it should
    Lens: /home/rjones/d/augeas/lenses/fstab.aug:36.12-.42:
      Last match: /home/rjones/d/augeas/lenses/fstab.aug:31.19-33.76:
      Not matching: /home/rjones/d/augeas/lenses/util.aug:111.22-.67:
    Error encountered at 1:68 (68 characters into string)
    <nodev,nosuid,noexec,relatime|=|,, 0 0\n>                   

Not sure whether we care.

[crobinso]

This works for me. However it doesn't parse:

/dev/mapper/vg00-vartmp /var/tmp xfs rw,nodev,nosuid,noexec,relatime,, 0 0

saying:

/home/rjones/d/augeas/lenses/tests/test_fstab.aug:187.2-199.3:exception thrown in test
/home/rjones/d/augeas/lenses/tests/test_fstab.aug:187.7-.99:exception: Iterated lens matched less than it should
    Lens: /home/rjones/d/augeas/lenses/fstab.aug:36.12-.42:
      Last match: /home/rjones/d/augeas/lenses/fstab.aug:31.19-33.76:
      Not matching: /home/rjones/d/augeas/lenses/util.aug:111.22-.67:
    Error encountered at 1:68 (68 characters into string)
    <nodev,nosuid,noexec,relatime|=|,, 0 0\n>                   

Not sure whether we care.

Good catch. I fixed the patch to test + address that now

[rwmjones]

Looks fine to me. Note I'm unable to merge stuff in Augeas.

[twied]

Question for someone with more insight than me: Are empty mount options filtered out by mount, or are they visible to the mount.type helpers? If the latter is the case, it might be preferential to allow empty mount options instead of allowing consecutive commas.

[crobinso]

In my testing, the multiple commas were ignored. Now looking at util-linux code the opstr parsing basically iterates over the string using ul_optstr_next: https://github.com/util-linux/util-linux/blob/master/lib/strutils.c#L1234

Option parsing stops at the first comma, and then next iteration strips all leading commas

[crobinso]

Updated now to deal with leading commas too