If `-o` is specified, output files are created in <dir>. Otherwise
they are created in the current working directory. The default path
-can be set with the 'format.outputDirectory' configuration option.
+can be set with the `format.outputDirectory` configuration option.
The `-o` option takes precedence over `format.outputDirectory`.
To store patches in the current working directory even when
`format.outputDirectory` points elsewhere, use `-o .`.
`--in-reply-to`, and the first patch mail, in this order. 'deep'
threading makes every mail a reply to the previous one.
+
-The default is `--no-thread`, unless the 'format.thread' configuration
+The default is `--no-thread`, unless the `format.thread` configuration
is set. If `--thread` is specified without a style, it defaults to the
-style specified by 'format.thread' if any, or else `shallow`.
+style specified by `format.thread` if any, or else `shallow`.
+
Beware that the default for 'git send-email' is to thread emails
itself. If you want `git format-patch` to take care of threading, you
Output an all-zero hash in each patch's From header instead
of the hash of the commit.
+--base=<commit>::
+ Record the base tree information to identify the state the
+ patch series applies to. See the BASE TREE INFORMATION section
+ below for details.
+
--root::
Treat the revision argument as a <revision range>, even if it
is just a single commit (that would normally be treated as a
5. Back in the compose window: add whatever other text you wish to the
message, complete the addressing and subject fields, and press send.
+BASE TREE INFORMATION
+---------------------
+
+The base tree information block is used for maintainers or third party
+testers to know the exact state the patch series applies to. It consists
+of the 'base commit', which is a well-known commit that is part of the
+stable part of the project history everybody else works off of, and zero
+or more 'prerequisite patches', which are well-known patches in flight
+that is not yet part of the 'base commit' that need to be applied on top
+of 'base commit' in topological order before the patches can be applied.
+
+The 'base commit' is shown as "base-commit: " followed by the 40-hex of
+the commit object name. A 'prerequisite patch' is shown as
+"prerequisite-patch-id: " followed by the 40-hex 'patch id', which can
+be obtained by passing the patch through the `git patch-id --stable`
+command.
+
+Imagine that on top of the public commit P, you applied well-known
+patches X, Y and Z from somebody else, and then built your three-patch
+series A, B, C, the history would be like:
+
+................................................
+---P---X---Y---Z---A---B---C
+................................................
+
+With `git format-patch --base=P -3 C` (or variants thereof, e.g. with
+`--cover-letter` of using `Z..C` instead of `-3 C` to specify the
+range), the base tree information block is shown at the end of the
+first message the command outputs (either the first patch, or the
+cover letter), like this:
+
+------------
+base-commit: P
+prerequisite-patch-id: X
+prerequisite-patch-id: Y
+prerequisite-patch-id: Z
+------------
+
+For non-linear topology, such as
+
+................................................
+---P---X---A---M---C
+ \ /
+ Y---Z---B
+................................................
+
+You can also use `git format-patch --base=P -3 C` to generate patches
+for A, B and C, and the identifiers for P, X, Y, Z are appended at the
+end of the first message.
+
+If set `--base=auto` in cmdline, it will track base commit automatically,
+the base commit will be the merge base of tip commit of the remote-tracking
+branch and revision-range specified in cmdline.
+For a local branch, you need to track a remote branch by `git branch
+--set-upstream-to` before using this option.
EXAMPLES
--------