git-interpret-trailers

git-interpret-trailers(1) =========================

NAME ---- git-interpret-trailers - Add or parse metadata in commit messages

SYNOPSIS --------

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

DESCRIPTION ----------- Add or parse trailer metadata at the end of the otherwise free-form part of a commit message, or any other kind of text.

A trailer in its simplest form is a key-value pair with a colon as a separator. The key consists of ASCII alphanumeric characters and hyphens (-). A trailer block consists of one or more trailers. The trailer block needs to be preceded by a blank line, where a blank line is either an empty or a whitespace-only line. For example, in the following commit message

subject

Lorem ipsum dolor sit amet, consectetur adipiscing elit.

Signed-off-by: Alice <alice@example.com>
Signed-off-by: Bob <bob@example.com>

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.<key-alias> 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, 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.

Let’s consider new trailers added with --trailer. By default, the new trailer will appear at the end of the trailer block. Also by default, this new trailer will only be added if the last trailer is different to it. A trailer block will be created with only that trailer if a trailer block does not already exist. Recall that a trailer block needs to be preceded by a blank line, so a blank line will be inserted before the new trailer block in that case.

This is how the new trailer is added: a <key>=<value> or <key>:<value> argument given using --trailer will be appended after the existing trailers. 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).

Existing trailers are extracted from the input by looking for the trailer block. A trailer block is 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 trailer block is by definition at the end of the commit message. The message in turn is either (i) at the end of the input, or (ii) the last non-whitespace lines before a line that starts with --- (followed by a space or the end of the line).

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 \<key-alias> 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".

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.

OTHER RULES -----------

What was covered in the previous section are the rules that are relevant for regular use. The following points are included for completeness.

OPTIONS ------- --in-place:: --no-in-place:: Edit the files in place. The default is --no-in-place.

--trim-empty

--no-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.

The default is --no-trim-empty.

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

--no-trailer
Specify a (\<key>, \<value>) pair that should be applied as a trailer to the inputs. See the description of this command. Can be given multiple times.

Use --no-trailer to reset the list.

--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.<key-alias>.where configuration variables and applies to all --trailer options until the next occurrence of --where or --no-where. Possible placements are after, before, end or start.

Use --no-where to clear the effect of any previous use of --where, such that the relevant configuration variables are no longer overridden.

--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.<key-alias>.ifExists configuration variables and applies to all --trailer options until the next occurrence of --if-exists or --no-if-exists. Possible actions are addIfDifferent, addIfDifferentNeighbor, add, replace and doNothing.

Use --no-if-exists to clear the effect of any previous use of --if-exists, such that the relevant configuration variables are no longer overridden.

--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.<key-alias>.ifMissing configuration variables and applies to all --trailer options until the next occurrence of --if-missing or --no-if-missing. Possible actions are doNothing or add.

Use --no-if-missing to clear the effect of any previous use of --if-missing, such that the relevant configuration variables are no longer overridden.

--only-trailers

--no-only-trailers
Output only the trailers, not any other parts of the input. The default is --no-only-trailers.

--only-input

--no-only-input
Output only trailers that exist in the input; do not add any from the command-line or by applying trailer.<key-alias> configuration variables. The default is --no-only-input.

--unfold

--no-unfold
If a trailer has a value that runs over multiple lines (aka "folded"), reformat the value into a single line. The default is --no-unfold.

--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.

There is no convenience alias to negate this alias.

--divider

--no-divider
Treat --- as the end of the commit message. This is the default. Use --no-divider when you know your input contains just the commit message itself (and not an email or the output of git-format-patch).

CONFIGURATION VARIABLES -----------------------

EXAMPLES --------

• 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 alice@example.com' --trailer 'sign: Bob bob@example.com' <msg.txt subject

  body text

  Signed-off-by: Alice alice@example.com Signed-off-by: Bob bob@example.com

• Use the --in-place option to edit a commit message file in place:

  $ cat msg.txt subject

  body text

  Signed-off-by: Bob bob@example.com $ git interpret-trailers --trailer 'Acked-by: Alice alice@example.com' --in-place msg.txt $ cat msg.txt subject

  body text

  Signed-off-by: Bob bob@example.com Acked-by: Alice alice@example.com

• 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 alice@example.com' --trailer 'Reviewed-by: Bob bob@example.com' 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 bob@example.com $ cat msg2.txt subject

  body text

  Signed-off-by: Alice alice@example.com $ git interpret-trailers --trailer sign <msg2.txt subject

  body text

  Signed-off-by: Alice alice@example.com

• 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 gitster@pobox.com Helped-by: Christian Couder christian.couder@gmail.com

• 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(1) 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

• Here we try to use three different trailer keys. But it fails because two of them are not recognized as trailer keys.

  $ cat msg.txt subject

  Skapad-på: some-branch Hash-in-v6.11: 45c12d3269fe48f22834320c782ffe86c3560f2c Reviewed-by: Alice alice@example.com $ git interpret-trailers --only-trailers <msg.txt $

Recall that a trailer key has to consist of only ASCII alphanumeric characters and hyphens, and this does not hold for the two first supposed trailer keys. And now none are recognized as trailers because the candidate trailer block has at least one non-trailer line, even though Reviewed-by is a valid trailer key. Recall that a trailer block has to either (i) be all trailers, or (ii) consist of at least one Git-generated or user-configured trailer (and some other conditions). And (ii) is not satisfied since we have not configured any trailer keys.

SEE ALSO -------- git-commit, git-format-patch, git-config

GIT --- Part of the git suite