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[v2,7/7] doc/git-log: clarify handling of merge commit diffs

Message ID 20200729201220.GG2989342@coredump.intra.peff.net (mailing list archive)
State New, archived
Headers show
Series making log --first-parent imply -m | expand

Commit Message

Jeff King July 29, 2020, 8:12 p.m. UTC 
It can be surprising that git-log doesn't show any diff for merge
commits by default. Arguably "--cc" would be a reasonable default, but
it's very expensive (which is why we turn it on for "git show" but not
for "git log"). Let's at least document the current behavior, including
the recent "--first-parent implies -m" case

Signed-off-by: Jeff King <peff@peff.net>
---
 Documentation/git-log.txt | 7 +++++++
 1 file changed, 7 insertions(+)
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Patch

diff --git a/Documentation/git-log.txt b/Documentation/git-log.txt
index 0a4c99e5f8..9ccba65469 100644
--- a/Documentation/git-log.txt
+++ b/Documentation/git-log.txt
@@ -117,6 +117,13 @@  DIFF FORMATTING
 By default, `git log` does not generate any diff output. The options
 below can be used to show the changes made by each commit.
 
+Note that unless one of `-c`, `--cc`, or `-m` is given, merge commits
+will never show a diff, even if a diff format like `--patch` is
+selected, nor will they match search options like `-S`. The exception is
+when `--first-parent` is in use, in which merges are treated like normal
+single-parent commits (this can be overridden by providing a
+combined-diff option or with `--no-diff-merges`).
+
 -c::
 	With this option, diff output for a merge commit
 	shows the differences from each of the parents to the merge result