git log -p -m: document -m and honor --first-parent

git log -p -m is used to show one merge entry per parent, with an
appropriate diff; this can be useful when examining histories where
full set of changes introduced by a merged branch is interesting, not
only the conflicts.

This patch properly documents the -m switch, which has so far been
mentioned only as a fairly special diff-tree flag.

It also makes the code show full patch entry only for the first parent
when --first-parent is used. Thus:

	git log -p -m --first-parent

will show the history from the "main branch perspective", while also
including full diff of changes introduced by other merged in branches.

Signed-off-by: Petr Baudis <pasky@suse.cz>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 9 insertions, 0 deletions

diff --git a/Documentation/git-log.txt b/Documentation/git-log.txt
index 0e39bb61ee..fb184ba186 100644
--- a/Documentation/git-log.txt
+++ b/Documentation/git-log.txt
@@ -118,6 +118,15 @@ git log master --not --remotes=*/master::
 	Shows all commits that are in local master but not in any remote
 	repository master branches.
 
+git log -p -m --first-parent::
+
+	Shows the history including change diffs, but only from the
+	"main branch" perspective, skipping commits that come from merged
+	branches, and showing full diffs of changes introduced by the merges.
+	This makes sense only when following a strict policy of merging all
+	topic branches when staying on a single integration branch.
+
+
 Discussion
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