In PR git-lfs#1870, which was based on the work in PR git-lfs#1822, we introduced
support for "lockable" files whose permissions would be managed by
several new Git LFS commands such as "git lfs post-checkout" and
"git lfs post-merge", both of which we register as Git hooks.

In commit 585befa of PRs git-lfs#1822 and git-lfs#1870
we added manual pages for these two commands.  (Although these PRs
also introduced the "git lfs post-commit" command, they did not
include a manual page for it, so we added one belatedly in commit
ae5d5b0 of PR git-lfs#4052.)

From the time it was written, our git-lfs-post-checkout(1) manual page has
indicated that the command accepts three arguments.  This accurately
reflects the fact that Git will invoke our hook command with parameters
specifying the SHAs from before and after the checkout operation, plus
a status flag indicating whether a branch checkout was performed or not.

However, our manual page does not explain what values these arguments
are expected to contain, other than by dint of the names given to the
arguments in the page's synopsis section.  We therefore expand our
description of the "git lfs post-checkout" command to detail the values
Git will provide in each of the three arguments.

We also take the opportunity to adjust the name of the second argument
to clarify that we expect this parameter to contain a Git revision SHA
and not the name of a Git reference such as a branch or tag.  As well,
we replace the underscores in the argument names with hyphens to match
the style we use in all our other manual pages for the names of command
parameters.

In PR git-lfs#1870, which was based on the work in PR git-lfs#1822, we introduced
support for "lockable" files whose permissions would be managed by
several new Git LFS commands such as "git lfs post-checkout" and
"git lfs post-merge", both of which we register as Git hooks.

In commit 585befa of PRs git-lfs#1822 and git-lfs#1870
we added manual pages for these two commands.  (Although these PRs
also introduced the "git lfs post-commit" command, they did not
include a manual page for it, so we added one belatedly in commit
ae5d5b0 of PR git-lfs#4052.)

From the time it was written, our git-lfs-post-merge(1) manual page has
indicated that the command accepts a single "<is_squash>" argument.
This accurately reflects the fact that Git will invoke our hook command
with a single flag parameter that indicates whether or not a squash merge
was performed.

However, our "git lfs post-merge" command disregards this parameter
entirely, so we adjust our manual page now to clarify that this command
requires no arguments and ignores the one provided by Git.