Update zfs-snapshot.8 to fix a small inaccuracy in the description of snapshot atomicity

[shawnbayern]

Fixes a small inaccuracy in the description of snapshot atomicity

zfs-snapshot(8) appears to contain a small error. The existing version reads "Snapshots are taken atomically, so that all snapshots correspond to the same moment in time." Per zfs_main.c, which in do_snapshot() simply loops over argv, this does not appear to be correct when multiple snapshots are specified explicitly on the command line. I believe the intent of the man page was to say that recursive snapshots are all created atomically.

This proposed change fixes that error. Because the existing statement may confuse some readers anyway, the commit also also adds a small amount of general explanatory information that may be helpful.

The change also adds an introductory sentence that summarizes what 'zfs snapshot' does in the first place. In that sentence, the text "different datasets" is intended to indicate that (again per the code) the same dataset cannot be specified multiple times on the command line.

Types of changes

• Documentation (a change to man pages or other documentation)

Checklist:

• I have updated the documentation accordingly.
• I have read the contributing document.
• All commit messages are properly formatted and contain Signed-off-by.

[shawnbayern]

I noticed that the automated check flagged another minor formatting problem, so I've committed a fix.

(I'm a law professor and thought the rules for formatting legal citations were strict, but by comparison they're not! :) )

[behlendorf]

@shawnbayern thanks!

[shawnbayern]

Sorry to waste your time, but checkstyle now seems to be failing because my recent commit messages were over 72 characters per line. (I knew to avoid that from the contributors' guide and avoided it in my initial writeup, but I think my last two commit messages were over that limit - sorry!) I'm not sure of the cleanest way to fix that on GitHub to satisfy the checkstyle script; should I produce a new branch? Thanks again for your help.

[behlendorf]

@shawnbayern no problem. You'll want to squash your commits and then force up the PR. This will kick of a new CI run. Something like this:

git checkout patch-1
git rebase -i master
# Do the squash
git push --force shawnbayern patch-1

[shawnbayern]

@behlendorf thanks again! I'll keep an eye out for any further problems.