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>

--skip=<number>

--since=<date>, --after=<date>

--since-as-filter=<date>

--until=<date>, --before=<date>

--author=<pattern>, --committer=<pattern>

--grep-reflog=<pattern>

--grep=<pattern>

--all-match

--invert-grep

-i, --regexp-ignore-case

--basic-regexp

-E, --extended-regexp

-F, --fixed-strings

-P, --perl-regexp

--remove-empty

--merges

--no-merges

--min-parents=<number>, --max-parents=<number>, --no-min-parents, --no-max-parents

--first-parent

--exclude-first-parent-only

--not

--all

--branches[=<pattern>]

--tags[=<pattern>]

--remotes[=<pattern>]

--glob=<glob-pattern>

--exclude=<glob-pattern>

--exclude-hidden=[fetch|receive|uploadpack]

--reflog

--alternate-refs

--single-worktree

--ignore-missing

--bisect

--stdin

--cherry-mark

--cherry-pick

--left-only, --right-only

--cherry

-g, --walk-reflogs

--merge

--boundary

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>

--simplify-by-decoration

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

The following options affect the way the simplification is performed:

Default mode

--show-pulls

--full-history

--dense

--sparse

--simplify-merges

--ancestry-path[=<commit>]

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:

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

          .-A---N---O
         /     /   /
        I---------D

--full-history without parent rewriting

        I  A  B  N  D  O  P  Q

--full-history with parent rewriting

          .-A---M---N---O---P---Q
         /     /   /   /   /
        I     B   /   D   /
         \   /   /   /   /
          `-------------'

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

--dense

--sparse

--simplify-merges

          .-A---M---N---O
         /     /       /
        I     B       D
         \   /       /
          `---------'

There is another simplification mode available:

--ancestry-path[=<commit>]

            D---E-------F
           /     \       \
          B---C---G---H---I---J
         /                     \
        A-------K---------------L--M

                E-------F
                 \       \
                  G---H---I---J
                               \
                                L--M

                E
                 \
                  G---H---I---J
                               \
                                L--M

                K---------------L--M

Before discussing another option, --show-pulls, we need to create a new example history.

A common problem users face when looking at simplified history is that a commit they know changed a file somehow does not appear in the file’s simplified history. Let’s demonstrate a new example and show how options such as --full-history and --simplify-merges works in that case:

          .-A---M-----C--N---O---P
         /     / \  \  \/   /   /
        I     B   \  R-'`-Z'   /
         \   /     \/         /
          \ /      /\        /
           `---X--'  `---Y--'

For this example, suppose I created file.txt which was modified by A, B, and X in different ways. The single-parent commits C, Z, and Y do not change file.txt. The merge commit M was created by resolving the merge conflict to include both changes from A and B and hence is not TREESAME to either. The merge commit R, however, was created by ignoring the contents of file.txt at M and taking only the contents of file.txt at X. Hence, R is TREESAME to X but not M. Finally, the natural merge resolution to create N is to take the contents of file.txt at R, so N is TREESAME to R but not C. The merge commits O and P are TREESAME to their first parents, but not to their second parents, Z and Y respectively.

When using the default mode, N and R both have a TREESAME parent, so those edges are walked and the others are ignored. The resulting history graph is:

        I---X

When using --full-history, Git walks every edge. This will discover the commits A and B and the merge M, but also will reveal the merge commits O and P. With parent rewriting, the resulting graph is:

          .-A---M--------N---O---P
         /     / \  \  \/   /   /
        I     B   \  R-'`--'   /
         \   /     \/         /
          \ /      /\        /
           `---X--'  `------'

Here, the merge commits O and P contribute extra noise, as they did not actually contribute a change to file.txt. They only merged a topic that was based on an older version of file.txt. This is a common issue in repositories using a workflow where many contributors work in parallel and merge their topic branches along a single trunk: many unrelated merges appear in the --full-history results.

When using the --simplify-merges option, the commits O and P disappear from the results. This is because the rewritten second parents of O and P are reachable from their first parents. Those edges are removed and then the commits look like single-parent commits that are TREESAME to their parent. This also happens to the commit N, resulting in a history view as follows:

          .-A---M--.
         /     /    \
        I     B      R
         \   /      /
          \ /      /
           `---X--'

In this view, we see all of the important single-parent changes from A, B, and X. We also see the carefully-resolved merge M and the not-so-carefully-resolved merge R. This is usually enough information to determine why the commits A and B "disappeared" from history in the default view. However, there are a few issues with this approach.

The first issue is performance. Unlike any previous option, the --simplify-merges option requires walking the entire commit history before returning a single result. This can make the option difficult to use for very large repositories.

The second issue is one of auditing. When many contributors are working on the same repository, it is important which merge commits introduced a change into an important branch. The problematic merge R above is not likely to be the merge commit that was used to merge into an important branch. Instead, the merge N was used to merge R and X into the important branch. This commit may have information about why the change X came to override the changes from A and B in its commit message.

--show-pulls

        I---X---R---N

          .-A---M--.   N
         /     /    \ /
        I     B      R
         \   /      /
          \ /      /
           `---X--'

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).