Merge branch 'lt/decorate'

* lt/decorate:
  rev-list documentation: clarify the two parts of history simplification
  Document "git log --simplify-by-decoration"
  Document "git log --source"
  revision traversal: '--simplify-by-decoration'
  Make '--decorate' set an explicit 'show_decorations' flag
  revision: make tree comparison functions take commits rather than trees
  Add a 'source' decorator for commits

Conflicts:
	Documentation/rev-list-options.txt

1 files changed, 54 insertions, 2 deletions

diff --git a/Documentation/rev-list-options.txt b/Documentation/rev-list-options.txt
index 68a253f977..6d7cf6d51f 100644
--- a/Documentation/rev-list-options.txt
+++ b/Documentation/rev-list-options.txt
@@ -285,8 +285,52 @@ See also linkgit:git-reflog[1].
 History Simplification
 ~~~~~~~~~~~~~~~~~~~~~~
 
-When optional paths are given, 'git rev-list' simplifies commits with
-various strategies, according to the options you have selected.
+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::
+
+	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.
+
+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
@@ -456,6 +500,14 @@ Note the major differences in `N` and `P` over '\--full-history':
   removed completely, because it had one parent and is TREESAME.
 --
 
+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
 ~~~~~~~~~~~~~~~~~