builtin/blame: destroy initialized commit_info only

[git.git] / Documentation / rev-list-options.txt

Commit Limiting
~~~~~~~~~~~~~~~

Besides specifying a range of commits that should be listed using the
special notations explained in the description, additional commit
limiting may be applied.

Using more options generally further limits the output (e.g.
`--since=<date1>` limits to commits newer than `<date1>`, and using it
with `--grep=<pattern>` further limits to commits whose log message
has a line that matches `<pattern>`), unless otherwise noted.

Note that these are applied before commit
ordering and formatting options, such as `--reverse`.

--

-<number>::
-n <number>::
--max-count=<number>::
        Limit the number of commits to output.

--skip=<number>::
        Skip 'number' commits before starting to show the commit output.

--since=<date>::
--after=<date>::
        Show commits more recent than a specific date.

--until=<date>::
--before=<date>::
        Show commits older than a specific date.

ifdef::git-rev-list[]
--max-age=<timestamp>::
--min-age=<timestamp>::
        Limit the commits output to specified time range.
endif::git-rev-list[]

--author=<pattern>::
--committer=<pattern>::
        Limit the commits output to ones with author/committer
        header lines that match the specified pattern (regular
        expression).  With more than one `--author=<pattern>`,
        commits whose author matches any of the given patterns are
        chosen (similarly for multiple `--committer=<pattern>`).

--grep-reflog=<pattern>::
        Limit the commits output to ones with reflog entries that
        match the specified pattern (regular expression). With
        more than one `--grep-reflog`, commits whose reflog message
        matches any of the given patterns are chosen.  It is an
        error to use this option unless `--walk-reflogs` is in use.

--grep=<pattern>::
        Limit the commits output to ones with log message that
        matches the specified pattern (regular expression).  With
        more than one `--grep=<pattern>`, commits whose message
        matches any of the given patterns are chosen (but see
        `--all-match`).
+
When `--show-notes` is in effect, the message from the notes as
if it is part of the log message.

--all-match::
        Limit the commits output to ones that match all given `--grep`,
        instead of ones that match at least one.

-i::
--regexp-ignore-case::
        Match the regular expression limiting patterns without regard to letter
        case.

--basic-regexp::
        Consider the limiting patterns to be basic regular expressions;
        this is the default.

-E::
--extended-regexp::
        Consider the limiting patterns to be extended regular expressions
        instead of the default basic regular expressions.

-F::
--fixed-strings::
        Consider the limiting patterns to be fixed strings (don't interpret
        pattern as a regular expression).

--perl-regexp::
        Consider the limiting patterns to be Perl-compatible regular expressions.
        Requires libpcre to be compiled in.

--remove-empty::
        Stop when a given path disappears from the tree.

--merges::
        Print only merge commits. This is exactly the same as `--min-parents=2`.

--no-merges::
        Do not print commits with more than one parent. This is
        exactly the same as `--max-parents=1`.

--min-parents=<number>::
--max-parents=<number>::
--no-min-parents::
--no-max-parents::
        Show only commits which have at least (or at most) that many parent
        commits. In particular, `--max-parents=1` is the same as `--no-merges`,
        `--min-parents=2` is the same as `--merges`.  `--max-parents=0`
        gives all root commits and `--min-parents=3` all octopus merges.
+
`--no-min-parents` and `--no-max-parents` reset these limits (to no limit)
again.  Equivalent forms are `--min-parents=0` (any commit has 0 or more
parents) and `--max-parents=-1` (negative numbers denote no upper limit).

--first-parent::
        Follow only the first parent commit upon seeing a merge
        commit.  This option can give a better overview when
        viewing the evolution of a particular topic branch,
        because merges into a topic branch tend to be only about
        adjusting to updated upstream from time to time, and
        this option allows you to ignore the individual commits
        brought in to your history by such a merge.

--not::
        Reverses the meaning of the '{caret}' prefix (or lack thereof)
        for all following revision specifiers, up to the next `--not`.

--all::
        Pretend as if all the refs in `refs/` are listed on the
        command line as '<commit>'.

--branches[=<pattern>]::
        Pretend as if all the refs in `refs/heads` are listed
        on the command line as '<commit>'. If '<pattern>' is given, limit
        branches to ones matching given shell glob. If pattern lacks '?',
        '{asterisk}', or '[', '/{asterisk}' at the end is implied.

--tags[=<pattern>]::
        Pretend as if all the refs in `refs/tags` are listed
        on the command line as '<commit>'. If '<pattern>' is given, limit
        tags to ones matching given shell glob. If pattern lacks '?', '{asterisk}',
        or '[', '/{asterisk}' at the end is implied.

--remotes[=<pattern>]::
        Pretend as if all the refs in `refs/remotes` are listed
        on the command line as '<commit>'. If '<pattern>' is given, limit
        remote-tracking branches to ones matching given shell glob.
        If pattern lacks '?', '{asterisk}', or '[', '/{asterisk}' at the end is implied.

--glob=<glob-pattern>::
        Pretend as if all the refs matching shell glob '<glob-pattern>'
        are listed on the command line as '<commit>'. Leading 'refs/',
        is automatically prepended if missing. If pattern lacks '?', '{asterisk}',
        or '[', '/{asterisk}' at the end is implied.

--ignore-missing::
        Upon seeing an invalid object name in the input, pretend as if
        the bad input was not given.

ifndef::git-rev-list[]
--bisect::
        Pretend as if the bad bisection ref `refs/bisect/bad`
        was listed and as if it was followed by `--not` and the good
        bisection refs `refs/bisect/good-*` on the command
        line.
endif::git-rev-list[]

--stdin::
        In addition to the '<commit>' listed on the command
        line, read them from the standard input. If a '--' separator is
        seen, stop reading commits and start reading paths to limit the
        result.

ifdef::git-rev-list[]
--quiet::
        Don't print anything to standard output.  This form
        is primarily meant to allow the caller to
        test the exit status to see if a range of objects is fully
        connected (or not).  It is faster than redirecting stdout
        to `/dev/null` as the output does not have to be formatted.
endif::git-rev-list[]

--cherry-mark::
        Like `--cherry-pick` (see below) but mark equivalent commits
        with `=` rather than omitting them, and inequivalent ones with `+`.

--cherry-pick::
        Omit any commit that introduces the same change as
        another commit on the ``other side'' when the set of
        commits are limited with symmetric difference.
+
For example, if you have two branches, `A` and `B`, a usual way
to list all commits on only one side of them is with
`--left-right` (see the example below in the description of
the `--left-right` option). However, it shows the commits that were
cherry-picked from the other branch (for example, ``3rd on b'' may be
cherry-picked from branch A). With this option, such pairs of commits are
excluded from the output.

--left-only::
--right-only::
        List only commits on the respective side of a symmetric range,
        i.e. only those which would be marked `<` resp. `>` by
        `--left-right`.
+
For example, `--cherry-pick --right-only A...B` omits those
commits from `B` which are in `A` or are patch-equivalent to a commit in
`A`. In other words, this lists the `+` commits from `git cherry A B`.
More precisely, `--cherry-pick --right-only --no-merges` gives the exact
list.

--cherry::
        A synonym for `--right-only --cherry-mark --no-merges`; useful to
        limit the output to the commits on our side and mark those that
        have been applied to the other side of a forked history with
        `git log --cherry upstream...mybranch`, similar to
        `git cherry upstream mybranch`.

-g::
--walk-reflogs::
        Instead of walking the commit ancestry chain, walk
        reflog entries from the most recent one to older ones.
        When this option is used you cannot specify commits to
        exclude (that is, '{caret}commit', 'commit1..commit2',
        nor 'commit1\...commit2' notations cannot be used).
+
With `--pretty` format other than `oneline` (for obvious reasons),
this causes the output to have two extra lines of information
taken from the reflog.  By default, 'commit@\{Nth}' notation is
used in the output.  When the starting commit is specified as
'commit@\{now}', output also uses 'commit@\{timestamp}' notation
instead.  Under `--pretty=oneline`, the commit message is
prefixed with this information on the same line.
This option cannot be combined with `--reverse`.
See also linkgit:git-reflog[1].

--merge::
        After a failed merge, show refs that touch files having a
        conflict and don't exist on all heads to merge.

--boundary::
        Output excluded boundary commits. Boundary commits are
        prefixed with `-`.

--

History Simplification
~~~~~~~~~~~~~~~~~~~~~~

Sometimes you are only interested in parts of the history, for example the
commits modifying a particular <path>. But there are two parts of
'History Simplification', one part is selecting the commits and the other
is how to do it, as there are various strategies to simplify the history.

The following options select the commits to be shown:

<paths>::
        Commits modifying the given <paths> are selected.

--simplify-by-decoration::
        Commits that are referred by some branch or tag are selected.

Note that extra commits can be shown to give a meaningful history.

The following options affect the way the simplification is performed:

Default mode::
        Simplifies the history to the simplest history explaining the
        final state of the tree. Simplest because it prunes some side
        branches if the end result is the same (i.e. merging branches
        with the same content)

--full-history::
        Same as the default mode, but does not prune some history.

--dense::
        Only the selected commits are shown, plus some to have a
        meaningful history.

--sparse::
        All commits in the simplified history are shown.

--simplify-merges::
        Additional option to `--full-history` to remove some needless
        merges from the resulting history, as there are no selected
        commits contributing to this merge.

--ancestry-path::
        When given a range of commits to display (e.g. 'commit1..commit2'
        or 'commit2 {caret}commit1'), only display commits that exist
        directly on the ancestry chain between the 'commit1' and
        'commit2', i.e. commits that are both descendants of 'commit1',
        and ancestors of 'commit2'.

A more detailed explanation follows.

Suppose you specified `foo` as the <paths>.  We shall call commits
that modify `foo` !TREESAME, and the rest TREESAME.  (In a diff
filtered for `foo`, they look different and equal, respectively.)

In the following, we will always refer to the same example history to
illustrate the differences between simplification settings.  We assume
that you are filtering for a file `foo` in this commit graph:
-----------------------------------------------------------------------
          .-A---M---N---O---P---Q
         /     /   /   /   /   /
        I     B   C   D   E   Y
         \   /   /   /   /   /
          `-------------'   X
-----------------------------------------------------------------------
The horizontal line of history A---Q is taken to be the first parent of
each merge.  The commits are:

* `I` is the initial commit, in which `foo` exists with contents
  ``asdf'', and a file `quux` exists with contents ``quux''. Initial
  commits are compared to an empty tree, so `I` is !TREESAME.

* In `A`, `foo` contains just ``foo''.

* `B` contains the same change as `A`.  Its merge `M` is trivial and
  hence TREESAME to all parents.

* `C` does not change `foo`, but its merge `N` changes it to ``foobar'',
  so it is not TREESAME to any parent.

* `D` sets `foo` to ``baz''. Its merge `O` combines the strings from
  `N` and `D` to ``foobarbaz''; i.e., it is not TREESAME to any parent.

* `E` changes `quux` to ``xyzzy'', and its merge `P` combines the
  strings to ``quux xyzzy''. `P` is TREESAME to `O`, but not to `E`.

* `X` is an independent root commit that added a new file `side`, and `Y`
  modified it. `Y` is TREESAME to `X`. Its merge `Q` added `side` to `P`, and
  `Q` is TREESAME to `P`, but not to `Y`.

`rev-list` walks backwards through history, including or excluding
commits based on whether `--full-history` and/or parent rewriting
(via `--parents` or `--children`) are used. The following settings
are available.

Default mode::
        Commits are included if they are not TREESAME to any parent
        (though this can be changed, see `--sparse` below).  If the
        commit was a merge, and it was TREESAME to one parent, follow
        only that parent.  (Even if there are several TREESAME
        parents, follow only one of them.)  Otherwise, follow all
        parents.
+
This results in:
+
-----------------------------------------------------------------------
          .-A---N---O
         /     /   /
        I---------D
-----------------------------------------------------------------------
+
Note how the rule to only follow the TREESAME parent, if one is
available, removed `B` from consideration entirely.  `C` was
considered via `N`, but is TREESAME.  Root commits are compared to an
empty tree, so `I` is !TREESAME.
+
Parent/child relations are only visible with `--parents`, but that does
not affect the commits selected in default mode, so we have shown the
parent lines.

--full-history without parent rewriting::
        This mode differs from the default in one point: always follow
        all parents of a merge, even if it is TREESAME to one of them.
        Even if more than one side of the merge has commits that are
        included, this does not imply that the merge itself is!  In
        the example, we get
+
-----------------------------------------------------------------------
        I  A  B  N  D  O  P  Q
-----------------------------------------------------------------------
+
`M` was excluded because it is TREESAME to both parents.  `E`,
`C` and `B` were all walked, but only `B` was !TREESAME, so the others
do not appear.
+
Note that without parent rewriting, it is not really possible to talk
about the parent/child relationships between the commits, so we show
them disconnected.

--full-history with parent rewriting::
        Ordinary commits are only included if they are !TREESAME
        (though this can be changed, see `--sparse` below).
+
Merges are always included.  However, their parent list is rewritten:
Along each parent, prune away commits that are not included
themselves.  This results in
+
-----------------------------------------------------------------------
          .-A---M---N---O---P---Q
         /     /   /   /   /
        I     B   /   D   /
         \   /   /   /   /
          `-------------'
-----------------------------------------------------------------------
+
Compare to `--full-history` without rewriting above.  Note that `E`
was pruned away because it is TREESAME, but the parent list of P was
rewritten to contain `E`'s parent `I`.  The same happened for `C` and
`N`, and `X`, `Y` and `Q`.

In addition to the above settings, you can change whether TREESAME
affects inclusion:

--dense::
        Commits that are walked are included if they are not TREESAME
        to any parent.

--sparse::
        All commits that are walked are included.
+
Note that without `--full-history`, this still simplifies merges: if
one of the parents is TREESAME, we follow only that one, so the other
sides of the merge are never walked.

--simplify-merges::
        First, build a history graph in the same way that
        `--full-history` with parent rewriting does (see above).
+
Then simplify each commit `C` to its replacement `C'` in the final
history according to the following rules:
+
--
* Set `C'` to `C`.
+
* Replace each parent `P` of `C'` with its simplification `P'`.  In
  the process, drop parents that are ancestors of other parents or that are
  root commits TREESAME to an empty tree, and remove duplicates, but take care
  to never drop all parents that we are TREESAME to.
+
* If after this parent rewriting, `C'` is a root or merge commit (has
  zero or >1 parents), a boundary commit, or !TREESAME, it remains.
  Otherwise, it is replaced with its only parent.
--
+
The effect of this is best shown by way of comparing to
`--full-history` with parent rewriting.  The example turns into:
+
-----------------------------------------------------------------------
          .-A---M---N---O
         /     /       /
        I     B       D
         \   /       /
          `---------'
-----------------------------------------------------------------------
+
Note the major differences in `N`, `P`, and `Q` over `--full-history`:
+
--
* `N`'s parent list had `I` removed, because it is an ancestor of the
  other parent `M`.  Still, `N` remained because it is !TREESAME.
+
* `P`'s parent list similarly had `I` removed.  `P` was then
  removed completely, because it had one parent and is TREESAME.
+
* `Q`'s parent list had `Y` simplified to `X`. `X` was then removed, because it
  was a TREESAME root. `Q` was then removed completely, because it had one
  parent and is TREESAME.
--

Finally, there is a fifth simplification mode available:

--ancestry-path::
        Limit the displayed commits to those directly on the ancestry
        chain between the ``from'' and ``to'' commits in the given commit
        range. I.e. only display commits that are ancestor of the ``to''
        commit and descendants of the ``from'' commit.
+
As an example use case, consider the following commit history:
+
-----------------------------------------------------------------------
            D---E-------F
           /     \       \
          B---C---G---H---I---J
         /                     \
        A-------K---------------L--M
-----------------------------------------------------------------------
+
A regular 'D..M' computes the set of commits that are ancestors of `M`,
but excludes the ones that are ancestors of `D`. This is useful to see
what happened to the history leading to `M` since `D`, in the sense
that ``what does `M` have that did not exist in `D`''. The result in this
example would be all the commits, except `A` and `B` (and `D` itself,
of course).
+
When we want to find out what commits in `M` are contaminated with the
bug introduced by `D` and need fixing, however, we might want to view
only the subset of 'D..M' that are actually descendants of `D`, i.e.
excluding `C` and `K`. This is exactly what the `--ancestry-path`
option does. Applied to the 'D..M' range, it results in:
+
-----------------------------------------------------------------------
                E-------F
                 \       \
                  G---H---I---J
                               \
                                L--M
-----------------------------------------------------------------------

The `--simplify-by-decoration` option allows you to view only the
big picture of the topology of the history, by omitting commits
that are not referenced by tags.  Commits are marked as !TREESAME
(in other words, kept after history simplification rules described
above) if (1) they are referenced by tags, or (2) they change the
contents of the paths given on the command line.  All other
commits are marked as TREESAME (subject to be simplified away).

ifdef::git-rev-list[]
Bisection Helpers
~~~~~~~~~~~~~~~~~

--bisect::
        Limit output to the one commit object which is roughly halfway between
        included and excluded commits. Note that the bad bisection ref
        `refs/bisect/bad` is added to the included commits (if it
        exists) and the good bisection refs `refs/bisect/good-*` are
        added to the excluded commits (if they exist). Thus, supposing there
        are no refs in `refs/bisect/`, if
+
-----------------------------------------------------------------------
        $ git rev-list --bisect foo ^bar ^baz
-----------------------------------------------------------------------
+
outputs 'midpoint', the output of the two commands
+
-----------------------------------------------------------------------
        $ git rev-list foo ^midpoint
        $ git rev-list midpoint ^bar ^baz
-----------------------------------------------------------------------
+
would be of roughly the same length.  Finding the change which
introduces a regression is thus reduced to a binary search: repeatedly
generate and test new 'midpoint's until the commit chain is of length
one.

--bisect-vars::
        This calculates the same as `--bisect`, except that refs in
        `refs/bisect/` are not used, and except that this outputs
        text ready to be eval'ed by the shell. These lines will assign the
        name of the midpoint revision to the variable `bisect_rev`, and the
        expected number of commits to be tested after `bisect_rev` is tested
        to `bisect_nr`, the expected number of commits to be tested if
        `bisect_rev` turns out to be good to `bisect_good`, the expected
        number of commits to be tested if `bisect_rev` turns out to be bad to
        `bisect_bad`, and the number of commits we are bisecting right now to
        `bisect_all`.

--bisect-all::
        This outputs all the commit objects between the included and excluded
        commits, ordered by their distance to the included and excluded
        commits. Refs in `refs/bisect/` are not used. The farthest
        from them is displayed first. (This is the only one displayed by
        `--bisect`.)
+
This is useful because it makes it easy to choose a good commit to
test when you want to avoid to test some of them for some reason (they
may not compile for example).
+
This option can be used along with `--bisect-vars`, in this case,
after all the sorted commit objects, there will be the same text as if
`--bisect-vars` had been used alone.
endif::git-rev-list[]


Commit Ordering
~~~~~~~~~~~~~~~

By default, the commits are shown in reverse chronological order.

--date-order::
        Show no parents before all of its children are shown, but
        otherwise show commits in the commit timestamp order.

--author-date-order::
        Show no parents before all of its children are shown, but
        otherwise show commits in the author timestamp order.

--topo-order::
        Show no parents before all of its children are shown, and
        avoid showing commits on multiple lines of history
        intermixed.
+
For example, in a commit history like this:
+
----------------------------------------------------------------

    ---1----2----4----7
        \              \
         3----5----6----8---

----------------------------------------------------------------
+
where the numbers denote the order of commit timestamps, `git
rev-list` and friends with `--date-order` show the commits in the
timestamp order: 8 7 6 5 4 3 2 1.
+
With `--topo-order`, they would show 8 6 5 3 7 4 2 1 (or 8 7 4 2 6 5
3 1); some older commits are shown before newer ones in order to
avoid showing the commits from two parallel development track mixed
together.

--reverse::
        Output the commits in reverse order.
        Cannot be combined with `--walk-reflogs`.

Object Traversal
~~~~~~~~~~~~~~~~

These options are mostly targeted for packing of Git repositories.

--objects::
        Print the object IDs of any object referenced by the listed
        commits.  `--objects foo ^bar` thus means ``send me
        all object IDs which I need to download if I have the commit
        object _bar_ but not _foo_''.

--objects-edge::
        Similar to `--objects`, but also print the IDs of excluded
        commits prefixed with a ``-'' character.  This is used by
        linkgit:git-pack-objects[1] to build ``thin'' pack, which records
        objects in deltified form based on objects contained in these
        excluded commits to reduce network traffic.

--unpacked::
        Only useful with `--objects`; print the object IDs that are not
        in packs.

--no-walk[=(sorted|unsorted)]::
        Only show the given commits, but do not traverse their ancestors.
        This has no effect if a range is specified. If the argument
        `unsorted` is given, the commits are shown in the order they were
        given on the command line. Otherwise (if `sorted` or no argument
        was given), the commits are shown in reverse chronological order
        by commit time.

--do-walk::
        Overrides a previous `--no-walk`.

Commit Formatting
~~~~~~~~~~~~~~~~~

ifdef::git-rev-list[]
Using these options, linkgit:git-rev-list[1] will act similar to the
more specialized family of commit log tools: linkgit:git-log[1],
linkgit:git-show[1], and linkgit:git-whatchanged[1]
endif::git-rev-list[]

include::pretty-options.txt[]

--relative-date::
        Synonym for `--date=relative`.

--date=(relative|local|default|iso|rfc|short|raw)::
        Only takes effect for dates shown in human-readable format, such
        as when using `--pretty`. `log.date` config variable sets a default
        value for the log command's `--date` option.
+
`--date=relative` shows dates relative to the current time,
e.g. ``2 hours ago''.
+
`--date=local` shows timestamps in user's local time zone.
+
`--date=iso` (or `--date=iso8601`) shows timestamps in ISO 8601 format.
+
`--date=rfc` (or `--date=rfc2822`) shows timestamps in RFC 2822
format, often found in email messages.
+
`--date=short` shows only the date, but not the time, in `YYYY-MM-DD` format.
+
`--date=raw` shows the date in the internal raw Git format `%s %z` format.
+
`--date=default` shows timestamps in the original time zone
(either committer's or author's).

ifdef::git-rev-list[]
--header::
        Print the contents of the commit in raw-format; each record is
        separated with a NUL character.
endif::git-rev-list[]

--parents::
        Print also the parents of the commit (in the form "commit parent...").
        Also enables parent rewriting, see 'History Simplification' below.

--children::
        Print also the children of the commit (in the form "commit child...").
        Also enables parent rewriting, see 'History Simplification' below.

ifdef::git-rev-list[]
--timestamp::
        Print the raw commit timestamp.
endif::git-rev-list[]

--left-right::
        Mark which side of a symmetric diff a commit is reachable from.
        Commits from the left side are prefixed with `<` and those from
        the right with `>`.  If combined with `--boundary`, those
        commits are prefixed with `-`.
+
For example, if you have this topology:
+
-----------------------------------------------------------------------
             y---b---b  branch B
            / \ /
           /   .
          /   / \
         o---x---a---a  branch A
-----------------------------------------------------------------------
+
you would get an output like this:
+
-----------------------------------------------------------------------
        $ git rev-list --left-right --boundary --pretty=oneline A...B

        >bbbbbbb... 3rd on b
        >bbbbbbb... 2nd on b
        <aaaaaaa... 3rd on a
        <aaaaaaa... 2nd on a
        -yyyyyyy... 1st on b
        -xxxxxxx... 1st on a
-----------------------------------------------------------------------

--graph::
        Draw a text-based graphical representation of the commit history
        on the left hand side of the output.  This may cause extra lines
        to be printed in between commits, in order for the graph history
        to be drawn properly.
+
This enables parent rewriting, see 'History Simplification' below.
+
This implies the `--topo-order` option by default, but the
`--date-order` option may also be specified.

ifdef::git-rev-list[]
--count::
        Print a number stating how many commits would have been
        listed, and suppress all other output.  When used together
        with `--left-right`, instead print the counts for left and
        right commits, separated by a tab. When used together with
        `--cherry-mark`, omit patch equivalent commits from these
        counts and print the count for equivalent commits separated
        by a tab.
endif::git-rev-list[]

ifndef::git-rev-list[]
Diff Formatting
~~~~~~~~~~~~~~~

Listed below are options that control the formatting of diff output.
Some of them are specific to linkgit:git-rev-list[1], however other diff
options may be given. See linkgit:git-diff-files[1] for more options.

-c::
        With this option, diff output for a merge commit
        shows the differences from each of the parents to the merge result
        simultaneously instead of showing pairwise diff between a parent
        and the result one at a time. Furthermore, it lists only files
        which were modified from all parents.

--cc::
        This flag implies the `-c` option and further compresses the
        patch output by omitting uninteresting hunks whose contents in
        the parents have only two variants and the merge result picks
        one of them without modification.

-m::
        This flag makes the merge commits show the full diff like
        regular commits; for each merge parent, a separate log entry
        and diff is generated. An exception is that only diff against
        the first parent is shown when `--first-parent` option is given;
        in that case, the output represents the changes the merge
        brought _into_ the then-current branch.

-r::
        Show recursive diffs.

-t::
        Show the tree objects in the diff output. This implies `-r`.
endif::git-rev-list[]