diff --git a/Documentation/format-patch-caveats.adoc b/Documentation/format-patch-caveats.adoc new file mode 100644 index 0000000000..807a65b885 --- /dev/null +++ b/Documentation/format-patch-caveats.adoc @@ -0,0 +1,33 @@ +The output from linkgit:git-format-patch[1] can lead to a different +commit message when applied with linkgit:git-am[1]. The patch that is +applied may also be different from the one that was generated, or patch +application may fail outright. +ifdef::git-am[] +See the <> section above for the syntactic rules. +endif::git-am[] + +ifndef::git-am[] +include::format-patch-end-of-commit-message.adoc[] +endif::git-am[] + +Note that this is especially problematic for unindented diffs that occur +in the commit message; the diff in the commit message might get applied +along with the patch section, or the patch application machinery might +trip up because the patch target doesn't apply. This could for example +be caused by a diff in a Markdown code block. + +The solution for this is to indent the diff or other text that could +cause problems. + +This loss of fidelity might be simple to notice if you are applying +patches directly from a mailbox. However, changes originating from Git +could be applied in bulk, in which case this would be much harder to +notice. This could for example be a Linux distribution which uses patch +files to apply changes on top of the commits from the upstream +repositories. This goes to show that this behavior does not only impact +email workflows. + +Given these limitations, one might be tempted to use a general-purpose +utility like patch(1) instead. However, patch(1) will not only look for +unindented diffs (like linkgit:git-am[1]) but will try to apply indented +diffs as well. diff --git a/Documentation/format-patch-end-of-commit-message.adoc b/Documentation/format-patch-end-of-commit-message.adoc new file mode 100644 index 0000000000..ec1ef79f5e --- /dev/null +++ b/Documentation/format-patch-end-of-commit-message.adoc @@ -0,0 +1,8 @@ +Any line that is of the form: + +* 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. 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`, 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] diff --git a/Documentation/git-send-email.adoc b/Documentation/git-send-email.adoc index 44ae2ed5bf..741f748614 100644 --- a/Documentation/git-send-email.adoc +++ b/Documentation/git-send-email.adoc @@ -692,6 +692,11 @@ Links of a few such community maintained helpers are: - https://github.com/AdityaGarg8/git-credential-email[git-msgraph] (cross platform client that can send emails using the Microsoft Graph API) +CAVEATS +------- + +include::format-patch-caveats.adoc[] + SEE ALSO -------- linkgit:git-format-patch[1], linkgit:git-imap-send[1], mbox(5)