Add a short paragraph explaining --ancestry-path, followed by a more
detailed example. This mirrors how the other history simplification options
are documented.
Signed-off-by: Johan Herland <johan@xxxxxxxxxxx>
---
Documentation/rev-list-options.txt | 50 ++++++++++++++++++++++++++++++++++-
1 files changed, 48 insertions(+), 2 deletions(-)
diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index 81815e1..a33dd00 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -384,6 +384,14 @@ Default mode::
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
@@ -511,8 +519,6 @@ 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.
-Finally, there is a fourth simplification mode available:
-
--simplify-merges::
First, build a history graph in the same way that
@@ -554,6 +560,46 @@ Note the major differences in `N` and `P` over '\--full-history':
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
--
1.7.0.4
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