I think there is a word missing now after the "as". Something like "as it" or "as they".

I think you can even drop the "these" here.

s/contains/contain/

Can remove that indefinite "It":

New committers are assumed to already be familiar...

Passive -> active:
s/will show/shows/

No "s" because of the plural "merges":
s/looks/look/

A note on "should": it's not always wrong. The wrong way to use it is when it implies the writer is not sure of what they are saying, like "the screen output should look like this". The right way is when you are making a recommendation: "You should always use strong passwords."

In this case, you've made it more imperative. It's not a recommendation, it's the way things are. Nice!

How about "must be" rather than "is"?

As above, probably better with s/$/must/

Redundant with the same word used in the next line. How about "process"?

It would be terrible if something were to happen and this old, broken, confusing merge process were to be accidentally deleted totally by accident and unintentionally.

Better with "For example, to merge:"

Nice!

As above, probably better as "must be".

This is one of those rare instances where "should" is appropriate. "can" makes it sound like it is not possible rather than something that is to be avoided.

Since we are here, break sentence:

Committing is now possible.  However, it is good

s/OK/okay/

Good, but the original sentence is poor and the writer probably misused i.e. when they mean e.g., another reason to avoid these.
Easy to split the sentence here:

vendor tree but not in the main tree.  These are things that

Redundant "like" and "for example".

import, like the vendor's <filename>Makefile</filename>s

Hard to keep track of what "it" means here. Rearrange:

Avoid setting up a <application>svnsync</application> mirror
unless there is a very good reason for it.

"many" and "multiple" are redundant. Remove "many".

s/the network/network/

Spell out numbers up to ten:

four to ten

I would keep "these" but lose "three", reason being that counts in text frequently are wrong after text is edited.

Or better, just say

There are several ways to do this:</para>

Missing "name" after "same".

s/adding to/adding these entries to/

"your" is okay here, because it is specific. Sometimes these are hard to avoid.

The original sentence is kind of misleading. Reading it does not mean it will be kept. How about

or save it elsewhere.</para>

s/processing/processing,/

s/email/email,/

End the sentence here:

class="fqdomainname">freefall.FreeBSD.org</systemitem>.</para>

The rest of the sentence is redundant.

s/commit/commit,/

Hm. The original is a complex and confusing sentence which appears to include irrelevant information.

The commit is from a PR submitted by John Smith.

<para>Commit a port, after working with```

<para>Committing some code which will be merged from```

This can be third-person:

Looking at the PR, the developer sees it is not an area of the tree they normally work in,
so they have the change reviewed by the <literal>arch</literal> mailing list.  Since the
change is complex, the developer opts to <acronym>MFC</acronym> after one month to
allow adequate testing.</para>

"Currently" isn't doing anything useful here.

s/Currently the/The/

s/When working on/Working on/

s/When trying/Trying/

s/you/a developer/

s/you/a developer/

s/be,/is,/

s/your queries/queries/

Remove that misused, ugly emdash:

settled. Remember, with a version control system we can

s/will/can/

This whole paragraph needs a rewrite.

s/theses/these/

s/are not/must not be/

s/are/must be kept/

This is a recommendation, so either "should be" or "must be", depending on how imperative you feel.

s/are/is/ (singular "support")

"a port's" is redundant and can be removed.

That it would.

I'll make a note of it for later.