git-interpret-trailers(1)

—

NAME

git-interpret-trailers - Add or parse structured information in commit messages

SYNOPSIS

bash

git interpret-trailers\n [--in-place] [--trim-empty]
\n
                        [(--trailer (<key>|<key-alias>)[(=|:)<value>])...]
\n
                        [--parse] [<file>...]

DESCRIPTION

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

bash

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:

bash

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

bash

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:

bash

key: This is a very long value, with spaces and
\n
  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.

OPTIONS

--in-place

--trim-empty

--trailer <key>[(=|:)<value>]

--where <placement>, --no-where

--if-exists <action>, --no-if-exists

--if-missing <action>, --no-if-missing

--only-trailers

--only-input

--unfold

--parse

--no-divider

CONFIGURATION VARIABLES

trailer.separators

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 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

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

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

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

trailer.<keyAlias>.ifexists

trailer.<keyAlias>.ifmissing

trailer.<keyAlias>.command

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

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.

EXAMPLES

bash

$ 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]>

bash

$ 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]>

bash

$ 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

bash

$ 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]>

bash

$ git config trailer.separators ":#"
$ git config trailer.fix.key "Fix #"
$ echo "subject" | git interpret-trailers --trailer fix=42
subject
Fix #42

bash

$ 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]>

bash

$ 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)

bash

$ 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)

bash

$ 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

Part of the git(1) suite