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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONFIGURATION VARIABLES | EXAMPLES | SEE ALSO | GIT | COLOPHON |
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GIT-INTERPRET-TRAILERS(1) Git Manual GIT-INTERPRET-TRAILERS(1)
git-interpret-trailers - Add or parse structured information in
commit messages
git interpret-trailers [--in-place] [--trim-empty]
[(--trailer (<key>|<key-alias>)[(=|:)<value>])...]
[--parse] [<file>...]
Add or parse trailer lines that look similar to RFC 822 e-mail
headers, at the end of the otherwise free-form part of a commit
message. For example, in the following commit message
subject
Lorem ipsum dolor sit amet, consectetur adipiscing elit.
Signed-off-by: Alice <[email protected]>
Signed-off-by: Bob <[email protected]>
the last two lines starting with "Signed-off-by" are trailers.
This command reads commit messages from either the <file>
arguments or the standard input if no <file> is specified. If
--parse is specified, the output consists of the parsed trailers
coming from the input, without influencing them with any command
line options or configuration variables.
Otherwise, this command applies trailer.* configuration variables
(which could potentially add new trailers, as well as reposition
them), as well as any command line arguments that can override
configuration variables (such as --trailer=... which could also
add new trailers), to each input file. The result is emitted on
the standard output.
This command can also operate on the output of
git-format-patch(1), which is more elaborate than a plain commit
message. Namely, such output includes a commit message (as above),
a "---" divider line, and a patch part. For these inputs, the
divider and patch parts are not modified by this command and are
emitted as is on the output, unless --no-divider is specified.
Some configuration variables control the way the --trailer
arguments are applied to each input and the way any existing
trailer in the input is changed. They also make it possible to
automatically add some trailers.
By default, a <key>=<value> or <key>:<value> argument given using
--trailer will be appended after the existing trailers only if the
last trailer has a different (<key>, <value>) pair (or if there is
no existing trailer). The <key> and <value> parts will be trimmed
to remove starting and trailing whitespace, and the resulting
trimmed <key> and <value> will appear in the output like this:
key: value
This means that the trimmed <key> and <value> will be separated by
': ' (one colon followed by one space).
For convenience, a <key-alias> can be configured to make using
--trailer shorter to type on the command line. This can be
configured using the trailer.<key-alias>.key configuration
variable. The <keyAlias> must be a prefix of the full <key>
string, although case sensitivity does not matter. For example, if
you have
trailer.sign.key "Signed-off-by: "
in your configuration, you only need to specify --trailer="sign:
foo" on the command line instead of --trailer="Signed-off-by:
foo".
By default the new trailer will appear at the end of all the
existing trailers. If there is no existing trailer, the new
trailer will appear at the end of the input. A blank line will be
added before the new trailer if there isn’t one already.
Existing trailers are extracted from the input by looking for a
group of one or more lines that (i) is all trailers, or (ii)
contains at least one Git-generated or user-configured trailer and
consists of at least 25% trailers. The group must be preceded by
one or more empty (or whitespace-only) lines. The group must
either be at the end of the input or be the last non-whitespace
lines before a line that starts with --- (followed by a space or
the end of the line).
When reading trailers, there can be no whitespace before or inside
the <key>, but any number of regular space and tab characters are
allowed between the <key> and the separator. There can be
whitespaces before, inside or after the <value>. The <value> may
be split over multiple lines with each subsequent line starting
with at least one whitespace, like the "folding" in RFC 822.
Example:
key: This is a very long value, with spaces and
newlines in it.
Note that trailers do not follow (nor are they intended to follow)
many of the rules for RFC 822 headers. For example they do not
follow the encoding rule.
--in-place
Edit the files in place.
--trim-empty
If the <value> part of any trailer contains only whitespace,
the whole trailer will be removed from the output. This
applies to existing trailers as well as new trailers.
--trailer <key>[(=|:)<value>]
Specify a (<key>, <value>) pair that should be applied as a
trailer to the inputs. See the description of this command.
--where <placement>, --no-where
Specify where all new trailers will be added. A setting
provided with --where overrides the trailer.where and any
applicable trailer.<keyAlias>.where configuration variables
and applies to all --trailer options until the next occurrence
of --where or --no-where. Upon encountering --no-where, clear
the effect of any previous use of --where, such that the
relevant configuration variables are no longer overridden.
Possible placements are after, before, end or start.
--if-exists <action>, --no-if-exists
Specify what action will be performed when there is already at
least one trailer with the same <key> in the input. A setting
provided with --if-exists overrides the trailer.ifExists and
any applicable trailer.<keyAlias>.ifExists configuration
variables and applies to all --trailer options until the next
occurrence of --if-exists or --no-if-exists. Upon encountering
'--no-if-exists, clear the effect of any previous use of
'--if-exists, such that the relevant configuration variables
are no longer overridden. Possible actions are addIfDifferent,
addIfDifferentNeighbor, add, replace and doNothing.
--if-missing <action>, --no-if-missing
Specify what action will be performed when there is no other
trailer with the same <key> in the input. A setting provided
with --if-missing overrides the trailer.ifMissing and any
applicable trailer.<keyAlias>.ifMissing configuration
variables and applies to all --trailer options until the next
occurrence of --if-missing or --no-if-missing. Upon
encountering '--no-if-missing, clear the effect of any
previous use of '--if-missing, such that the relevant
configuration variables are no longer overridden. Possible
actions are doNothing or add.
--only-trailers
Output only the trailers, not any other parts of the input.
--only-input
Output only trailers that exist in the input; do not add any
from the command-line or by applying trailer.* configuration
variables.
--unfold
If a trailer has a value that runs over multiple lines (aka
"folded"), reformat the value into a single line.
--parse
A convenience alias for --only-trailers --only-input --unfold.
This makes it easier to only see the trailers coming from the
input without influencing them with any command line options
or configuration variables, while also making the output
machine-friendly with --unfold.
--no-divider
Do not treat --- as the end of the commit message. Use this
when you know your input contains just the commit message
itself (and not an email or the output of git format-patch).
Everything below this line in this section is selectively included
from the git-config(1) documentation. The content is the same as
what’s found there:
trailer.separators
This option tells which characters are recognized as trailer
separators. By default only : is recognized as a trailer
separator, except that = is always accepted on the command
line for compatibility with other git commands.
The first character given by this option will be the default
character used when another separator is not specified in the
config for this trailer.
For example, if the value for this option is "%=$", then only
lines using the format <key><sep><value> with <sep> containing
%, = or $ and then spaces will be considered trailers. And %
will be the default separator used, so by default trailers
will appear like: <key>% <value> (one percent sign and one
space will appear between the key and the value).
trailer.where
This option tells where a new trailer will be added.
This can be end, which is the default, start, after or before.
If it is end, then each new trailer will appear at the end of
the existing trailers.
If it is start, then each new trailer will appear at the
start, instead of the end, of the existing trailers.
If it is after, then each new trailer will appear just after
the last trailer with the same <key>.
If it is before, then each new trailer will appear just before
the first trailer with the same <key>.
trailer.ifexists
This option makes it possible to choose what action will be
performed when there is already at least one trailer with the
same <key> in the input.
The valid values for this option are: addIfDifferentNeighbor
(this is the default), addIfDifferent, add, replace or
doNothing.
With addIfDifferentNeighbor, a new trailer will be added only
if no trailer with the same (<key>, <value>) pair is above or
below the line where the new trailer will be added.
With addIfDifferent, a new trailer will be added only if no
trailer with the same (<key>, <value>) pair is already in the
input.
With add, a new trailer will be added, even if some trailers
with the same (<key>, <value>) pair are already in the input.
With replace, an existing trailer with the same <key> will be
deleted and the new trailer will be added. The deleted trailer
will be the closest one (with the same <key>) to the place
where the new one will be added.
With doNothing, nothing will be done; that is no new trailer
will be added if there is already one with the same <key> in
the input.
trailer.ifmissing
This option makes it possible to choose what action will be
performed when there is not yet any trailer with the same
<key> in the input.
The valid values for this option are: add (this is the
default) and doNothing.
With add, a new trailer will be added.
With doNothing, nothing will be done.
trailer.<keyAlias>.key
Defines a <keyAlias> for the <key>. The <keyAlias> must be a
prefix (case does not matter) of the <key>. For example, in
git config trailer.ack.key "Acked-by" the "Acked-by" is the
<key> and the "ack" is the <keyAlias>. This configuration
allows the shorter --trailer "ack:..." invocation on the
command line using the "ack" <keyAlias> instead of the longer
--trailer "Acked-by:...".
At the end of the <key>, a separator can appear and then some
space characters. By default the only valid separator is :,
but this can be changed using the trailer.separators config
variable.
If there is a separator in the key, then it overrides the
default separator when adding the trailer.
trailer.<keyAlias>.where
This option takes the same values as the trailer.where
configuration variable and it overrides what is specified by
that option for trailers with the specified <keyAlias>.
trailer.<keyAlias>.ifexists
This option takes the same values as the trailer.ifexists
configuration variable and it overrides what is specified by
that option for trailers with the specified <keyAlias>.
trailer.<keyAlias>.ifmissing
This option takes the same values as the trailer.ifmissing
configuration variable and it overrides what is specified by
that option for trailers with the specified <keyAlias>.
trailer.<keyAlias>.command
Deprecated in favor of trailer.<keyAlias>.cmd. This option
behaves in the same way as trailer.<keyAlias>.cmd, except that
it doesn’t pass anything as argument to the specified command.
Instead the first occurrence of substring $ARG is replaced by
the <value> that would be passed as argument.
Note that $ARG in the user’s command is only replaced once and
that the original way of replacing $ARG is not safe.
When both trailer.<keyAlias>.cmd and
trailer.<keyAlias>.command are given for the same <keyAlias>,
trailer.<keyAlias>.cmd is used and trailer.<keyAlias>.command
is ignored.
trailer.<keyAlias>.cmd
This option can be used to specify a shell command that will
be called once to automatically add a trailer with the
specified <keyAlias>, and then called each time a --trailer
<keyAlias>=<value> argument is specified to modify the <value>
of the trailer that this option would produce.
When the specified command is first called to add a trailer
with the specified <keyAlias>, the behavior is as if a special
--trailer <keyAlias>=<value> argument was added at the
beginning of the "git interpret-trailers" command, where
<value> is taken to be the standard output of the command with
any leading and trailing whitespace trimmed off.
If some --trailer <keyAlias>=<value> arguments are also passed
on the command line, the command is called again once for each
of these arguments with the same <keyAlias>. And the <value>
part of these arguments, if any, will be passed to the command
as its first argument. This way the command can produce a
<value> computed from the <value> passed in the --trailer
<keyAlias>=<value> argument.
• Configure a sign trailer with a Signed-off-by key, and then
add two of these trailers to a commit message file:
$ git config trailer.sign.key "Signed-off-by"
$ cat msg.txt
subject
body text
$ git interpret-trailers --trailer 'sign: Alice <[email protected]>' --trailer 'sign: Bob <[email protected]>' <msg.txt
subject
body text
Signed-off-by: Alice <[email protected]>
Signed-off-by: Bob <[email protected]>
• Use the --in-place option to edit a commit message file in
place:
$ cat msg.txt
subject
body text
Signed-off-by: Bob <[email protected]>
$ git interpret-trailers --trailer 'Acked-by: Alice <[email protected]>' --in-place msg.txt
$ cat msg.txt
subject
body text
Signed-off-by: Bob <[email protected]>
Acked-by: Alice <[email protected]>
• Extract the last commit as a patch, and add a Cc and a
Reviewed-by trailer to it:
$ git format-patch -1
0001-foo.patch
$ git interpret-trailers --trailer 'Cc: Alice <[email protected]>' --trailer 'Reviewed-by: Bob <[email protected]>' 0001-foo.patch >0001-bar.patch
• Configure a sign trailer with a command to automatically add a
'Signed-off-by: ' with the author information only if there is
no 'Signed-off-by: ' already, and show how it works:
$ cat msg1.txt
subject
body text
$ git config trailer.sign.key "Signed-off-by: "
$ git config trailer.sign.ifmissing add
$ git config trailer.sign.ifexists doNothing
$ git config trailer.sign.cmd 'echo "$(git config user.name) <$(git config user.email)>"'
$ git interpret-trailers --trailer sign <msg1.txt
subject
body text
Signed-off-by: Bob <[email protected]>
$ cat msg2.txt
subject
body text
Signed-off-by: Alice <[email protected]>
$ git interpret-trailers --trailer sign <msg2.txt
subject
body text
Signed-off-by: Alice <[email protected]>
• Configure a fix trailer with a key that contains a # and no
space after this character, and show how it works:
$ git config trailer.separators ":#"
$ git config trailer.fix.key "Fix #"
$ echo "subject" | git interpret-trailers --trailer fix=42
subject
Fix #42
• Configure a help trailer with a cmd use a script
glog-find-author which search specified author identity from
git log in git repository and show how it works:
$ cat ~/bin/glog-find-author
#!/bin/sh
test -n "$1" && git log --author="$1" --pretty="%an <%ae>" -1 || true
$ cat msg.txt
subject
body text
$ git config trailer.help.key "Helped-by: "
$ git config trailer.help.ifExists "addIfDifferentNeighbor"
$ git config trailer.help.cmd "~/bin/glog-find-author"
$ git interpret-trailers --trailer="help:Junio" --trailer="help:Couder" <msg.txt
subject
body text
Helped-by: Junio C Hamano <[email protected]>
Helped-by: Christian Couder <[email protected]>
• Configure a ref trailer with a cmd use a script glog-grep to
grep last relevant commit from git log in the git repository
and show how it works:
$ cat ~/bin/glog-grep
#!/bin/sh
test -n "$1" && git log --grep "$1" --pretty=reference -1 || true
$ cat msg.txt
subject
body text
$ git config trailer.ref.key "Reference-to: "
$ git config trailer.ref.ifExists "replace"
$ git config trailer.ref.cmd "~/bin/glog-grep"
$ git interpret-trailers --trailer="ref:Add copyright notices." <msg.txt
subject
body text
Reference-to: 8bc9a0c769 (Add copyright notices., 2005-04-07)
• Configure a see trailer with a command to show the subject of
a commit that is related, and show how it works:
$ cat msg.txt
subject
body text
see: HEAD~2
$ cat ~/bin/glog-ref
#!/bin/sh
git log -1 --oneline --format="%h (%s)" --abbrev-commit --abbrev=14
$ git config trailer.see.key "See-also: "
$ git config trailer.see.ifExists "replace"
$ git config trailer.see.ifMissing "doNothing"
$ git config trailer.see.cmd "glog-ref"
$ git interpret-trailers --trailer=see <msg.txt
subject
body text
See-also: fe3187489d69c4 (subject of related commit)
• Configure a commit template with some trailers with empty
values (using sed to show and keep the trailing spaces at the
end of the trailers), then configure a commit-msg hook that
uses git interpret-trailers to remove trailers with empty
values and to add a git-version trailer:
$ cat temp.txt
***subject***
***message***
Fixes: Z
Cc: Z
Reviewed-by: Z
Signed-off-by: Z
$ sed -e 's/ Z$/ /' temp.txt > commit_template.txt
$ git config commit.template commit_template.txt
$ cat .git/hooks/commit-msg
#!/bin/sh
git interpret-trailers --trim-empty --trailer "git-version: \$(git describe)" "\$1" > "\$1.new"
mv "\$1.new" "\$1"
$ chmod +x .git/hooks/commit-msg
git-commit(1), git-format-patch(1), git-config(1)
Part of the git(1) suite
This page is part of the git (Git distributed version control
system) project. Information about the project can be found at
⟨http://git-scm.com/⟩. If you have a bug report for this manual
page, see ⟨http://git-scm.com/community⟩. This page was obtained
from the project's upstream Git repository
⟨https://github.com/git/git.git⟩ on 2025-08-11. (At that time,
the date of the most recent commit that was found in the
repository was 2025-08-07.) If you discover any rendering
problems in this HTML version of the page, or you believe there is
a better or more up-to-date source for the page, or you have
corrections or improvements to the information in this COLOPHON
(which is not part of the original manual page), send a mail to
[email protected]
Git 2.51.0.rc1 2025-08-07 GIT-INTERPRET-TRAILERS(1)
Pages that refer to this page: git(1), git-commit(1), git-diff-tree(1), git-for-each-ref(1), git-log(1), git-rev-list(1), git-shortlog(1), git-show(1), git-tag(1), gitglossary(7)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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