Split git rev-parse --show-toplevel --git-dir on newline

git rev-parse --show-toplevel --git-dir returns the top
level directory and the .git directory on two seperate lines.

Splitting needs to happen explicitly on a newline, or else
paths with spaces will be parsed incorrectly.

Change-Id: Ie851d31ef55be63213fe8dc445f92af1b7a33f7d
Preserve merges when doing a rebase

When a person is using git-review after having merged in a branch, the
default rebase behavior as currently implemented will rebase all of the
commits that are inside of the merge. This is almost never what someone
wants to do.

Add -p to the rebase commands which will tell git to preserve the merges
and only rebase the merge commit itself.

Explicitly preserve original SHA1 from before the rebase, since git may
not set ORIG_HEAD as expected depending the operations performed.

Change-Id: I8a5f0307113cd0cf0d08c664c13a0676400bd05c
Remove empty lines from git log output

assert_one_change would falsely believe there was a commit when git log returned empty input
because python's strip method returns an array containing an empty string if nothing matches the separator
for example = "".split("\n") returns [''].

I remove empty strings to allow the check to respond to no non-pushed commits

Change-Id: I0d5608acb1728e77f20d9de71c6c23ec4da1c798
Merge "Split git rev-parse --show-toplevel --git-dir on newline"
Merge "Remove empty lines from git log output"
Merge "Preserve merges when doing a rebase"
Ignore content of merge commits in reporting

When we report changes that are going to be submitted, the results of
merging a giant branch into the current one is TERRIFYING, as it shows
every commit in the branch.

Exclude all changes that are already on branches in the remote so
that only the merge commit and its first parent are shown, which
should make the output less crazy-inducing.

Change-Id: I461f3eb23642deaf2caded631291414ae6997a91
Merge "Ignore content of merge commits in reporting"
Correct .Fl typo WRT --compare in the manual page

.Fl includes a dash for free when listing command line options, so
replace a typo of ---compare with --compare in the manual page.

Change-Id: Icaa6d87e954ebba75d534ed96f3632d80077f762