From a454cdca42fda0afaade73d7e90010289d1e7ba8 Mon Sep 17 00:00:00 2001 From: Kristoffer Haugsbakk Date: Thu, 12 Feb 2026 23:28:23 +0100 Subject: doc: add caveat about round-tripping format-patch MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit 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 Reported-by: Christoph Anton Mitterer Reported-by: Matheus Tavares Reported-by: Chris Packham Helped-by: Jakob Haufe Helped-by: Phillip Wood Signed-off-by: Kristoffer Haugsbakk Signed-off-by: Junio C Hamano --- Documentation/git-am.adoc | 19 ++++++++++++------- 1 file changed, 12 insertions(+), 7 deletions(-) (limited to 'Documentation/git-am.adoc') diff --git a/Documentation/git-am.adoc b/Documentation/git-am.adoc index 0c94776e29..972398d457 100644 --- a/Documentation/git-am.adoc +++ b/Documentation/git-am.adoc @@ -233,6 +233,7 @@ applying. create an empty commit with the contents of the e-mail message as its log message. +[[discussion]] DISCUSSION ---------- @@ -252,14 +253,11 @@ where the patch begins. Excess whitespace at the end of each line is automatically stripped. The patch is expected to be inline, directly following the -message. Any line that is of the form: +message. +include::format-patch-end-of-commit-message.adoc[] -* three-dashes and end-of-line, or -* a line that begins with "diff -", or -* a line that begins with "Index: " - -is taken as the beginning of a patch, and the commit log message -is terminated before the first occurrence of such a line. +This means that the contents of the commit message can inadvertently +interrupt the processing (see the <> section below). When initially invoking `git am`, you give it the names of the mailboxes to process. Upon seeing the first patch that does not apply, it @@ -283,6 +281,13 @@ commits, like running 'git am' on the wrong branch or an error in the commits that is more easily fixed by changing the mailbox (e.g. errors in the "From:" lines). +[[caveats]] +CAVEATS +------- + +:git-am: 1 +include::format-patch-caveats.adoc[] + HOOKS ----- This command can run `applypatch-msg`, `pre-applypatch`, -- cgit v1.3-5-g9baa