From a454cdca42fda0afaade73d7e90010289d1e7ba8 Mon Sep 17 00:00:00 2001
From: Kristoffer Haugsbakk <code@khaugsbakk.name>
Date: Thu, 12 Feb 2026 23:28:23 +0100
Subject: doc: add caveat about round-tripping format-patch
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git-format-patch(1) and git-am(1) deal with formatting commits as
patches and applying them, respectively. Naturally they use a few
delimiters to mark where the commit message ends. This can lead to
surprising behavior when these delimiters are used in the commit
message itself.

git-format-patch(1) will accept any commit message and not warn or error
about these delimiters being used.[1]

Especially problematic is the presence of unindented diffs in the commit
message; the patch machinery will naturally (since the commit message
has ended) try to apply that diff and everything after it.[2]

It is unclear whether any commands in this chain will learn to warn
about this. One concern could be that users have learned to rely on
the three-dash line rule to conveniently add extra-commit message
information in the commit message, knowing that git-am(1) will
ignore it.[4]

All of this is covered already, technically. However, we should spell
out the implications.

† 1: There is also git-commit(1) to consider. However, making that
     command warn or error out over such delimiters would be disruptive
     to all Git users who never use email in their workflow.
† 2: Recently patch(1) caused this issue for a project, but it was noted
     that git-am(1) has the same behavior[3]
† 3: https://github.com/i3/i3/pull/6564#issuecomment-3858381425
† 4: https://lore.kernel.org/git/xmqqldh4b5y2.fsf@gitster.g/
     https://lore.kernel.org/git/V3_format-patch_caveats.354@msgid.xyz/

Reported-by: Matthias Beyer <mail@beyermatthias.de>
Reported-by: Christoph Anton Mitterer <calestyo@scientia.org>
Reported-by: Matheus Tavares <matheus.tavb@gmail.com>
Reported-by: Chris Packham <judge.packham@gmail.com>
Helped-by: Jakob Haufe <sur5r@sur5r.net>
Helped-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Kristoffer Haugsbakk <code@khaugsbakk.name>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
---
 Documentation/git-format-patch.adoc | 4 ++++
 1 file changed, 4 insertions(+)

(limited to 'Documentation/git-format-patch.adoc')

diff --git a/Documentation/git-format-patch.adoc b/Documentation/git-format-patch.adoc
index 9a7807ca71..bac9b818f3 100644
--- a/Documentation/git-format-patch.adoc
+++ b/Documentation/git-format-patch.adoc
@@ -798,6 +798,10 @@ if they are part of the requested range. A simple "patch" does not
 include enough information for the receiving end to reproduce the same
 merge commit.
 
+=== PATCH APPLICATION
+
+include::format-patch-caveats.adoc[]
+
 SEE ALSO
 --------
 linkgit:git-am[1], linkgit:git-send-email[1]
-- 
cgit v1.3

