diff --git a/Documentation/pretty-formats.txt b/Documentation/pretty-formats.txt
index 7bfffae765..079598307a 100644
--- a/Documentation/pretty-formats.txt
+++ b/Documentation/pretty-formats.txt
@@ -102,120 +102,160 @@ The title was >>t4119: test autocomputing -p<n> for traditional diff input.<<
 +
 The placeholders are:
 
-- '%H': commit hash
-- '%h': abbreviated commit hash
-- '%T': tree hash
-- '%t': abbreviated tree hash
-- '%P': parent hashes
-- '%p': abbreviated parent hashes
-- '%an': author name
-- '%aN': author name (respecting .mailmap, see linkgit:git-shortlog[1]
-  or linkgit:git-blame[1])
-- '%ae': author email
-- '%aE': author email (respecting .mailmap, see
-  linkgit:git-shortlog[1] or linkgit:git-blame[1])
-- '%ad': author date (format respects --date= option)
-- '%aD': author date, RFC2822 style
-- '%ar': author date, relative
-- '%at': author date, UNIX timestamp
-- '%ai': author date, ISO 8601-like format
-- '%aI': author date, strict ISO 8601 format
-- '%cn': committer name
-- '%cN': committer name (respecting .mailmap, see
-  linkgit:git-shortlog[1] or linkgit:git-blame[1])
-- '%ce': committer email
-- '%cE': committer email (respecting .mailmap, see
-  linkgit:git-shortlog[1] or linkgit:git-blame[1])
-- '%cd': committer date (format respects --date= option)
-- '%cD': committer date, RFC2822 style
-- '%cr': committer date, relative
-- '%ct': committer date, UNIX timestamp
-- '%ci': committer date, ISO 8601-like format
-- '%cI': committer date, strict ISO 8601 format
-- '%d': ref names, like the --decorate option of linkgit:git-log[1]
-- '%D': ref names without the " (", ")" wrapping.
-- '%S': ref name given on the command line by which the commit was reached
-  (like `git log --source`), only works with `git log`
-- '%e': encoding
-- '%s': subject
-- '%f': sanitized subject line, suitable for a filename
-- '%b': body
-- '%B': raw body (unwrapped subject and body)
+- Placeholders that expand to a single literal character:
+'%n':: newline
+'%%':: a raw '%'
+'%x00':: print a byte from a hex code
+
+- Placeholders that affect formatting of later placeholders:
+'%Cred':: switch color to red
+'%Cgreen':: switch color to green
+'%Cblue':: switch color to blue
+'%Creset':: reset color
+'%C(...)':: color specification, as described under Values in the
+	    "CONFIGURATION FILE" section of linkgit:git-config[1].  By
+	    default, colors are shown only when enabled for log output
+	    (by `color.diff`, `color.ui`, or `--color`, and respecting
+	    the `auto` settings of the former if we are going to a
+	    terminal). `%C(auto,...)` is accepted as a historical
+	    synonym for the default (e.g., `%C(auto,red)`). Specifying
+	    `%C(always,...)` will show the colors even when color is
+	    not otherwise enabled (though consider just using
+	    `--color=always` to enable color for the whole output,
+	    including this format and anything else git might color).
+	    `auto` alone (i.e. `%C(auto)`) will turn on auto coloring
+	    on the next placeholders until the color is switched
+	    again.
+'%m':: left (`<`), right (`>`) or boundary (`-`) mark
+'%w([<w>[,<i1>[,<i2>]]])':: switch line wrapping, like the -w option of
+			    linkgit:git-shortlog[1].
+'%<(<N>[,trunc|ltrunc|mtrunc])':: make the next placeholder take at
+				  least N columns, padding spaces on
+				  the right if necessary.  Optionally
+				  truncate at the beginning (ltrunc),
+				  the middle (mtrunc) or the end
+				  (trunc) if the output is longer than
+				  N columns.  Note that truncating
+				  only works correctly with N >= 2.
+'%<|(<N>)':: make the next placeholder take at least until Nth
+	     columns, padding spaces on the right if necessary
+'%>(<N>)', '%>|(<N>)':: similar to '%<(<N>)', '%<|(<N>)' respectively,
+			but padding spaces on the left
+'%>>(<N>)', '%>>|(<N>)':: similar to '%>(<N>)', '%>|(<N>)'
+			  respectively, except that if the next
+			  placeholder takes more spaces than given and
+			  there are spaces on its left, use those
+			  spaces
+'%><(<N>)', '%><|(<N>)':: similar to '%<(<N>)', '%<|(<N>)'
+			  respectively, but padding both sides
+			  (i.e. the text is centered)
+
+- Placeholders that expand to information extracted from the commit:
+'%H':: commit hash
+'%h':: abbreviated commit hash
+'%T':: tree hash
+'%t':: abbreviated tree hash
+'%P':: parent hashes
+'%p':: abbreviated parent hashes
+'%an':: author name
+'%aN':: author name (respecting .mailmap, see linkgit:git-shortlog[1]
+	or linkgit:git-blame[1])
+'%ae':: author email
+'%aE':: author email (respecting .mailmap, see linkgit:git-shortlog[1]
+	or linkgit:git-blame[1])
+'%ad':: author date (format respects --date= option)
+'%aD':: author date, RFC2822 style
+'%ar':: author date, relative
+'%at':: author date, UNIX timestamp
+'%ai':: author date, ISO 8601-like format
+'%aI':: author date, strict ISO 8601 format
+'%cn':: committer name
+'%cN':: committer name (respecting .mailmap, see
+	linkgit:git-shortlog[1] or linkgit:git-blame[1])
+'%ce':: committer email
+'%cE':: committer email (respecting .mailmap, see
+	linkgit:git-shortlog[1] or linkgit:git-blame[1])
+'%cd':: committer date (format respects --date= option)
+'%cD':: committer date, RFC2822 style
+'%cr':: committer date, relative
+'%ct':: committer date, UNIX timestamp
+'%ci':: committer date, ISO 8601-like format
+'%cI':: committer date, strict ISO 8601 format
+'%d':: ref names, like the --decorate option of linkgit:git-log[1]
+'%D':: ref names without the " (", ")" wrapping.
+'%S':: ref name given on the command line by which the commit was reached
+       (like `git log --source`), only works with `git log`
+'%e':: encoding
+'%s':: subject
+'%f':: sanitized subject line, suitable for a filename
+'%b':: body
+'%B':: raw body (unwrapped subject and body)
 ifndef::git-rev-list[]
-- '%N': commit notes
+'%N':: commit notes
 endif::git-rev-list[]
-- '%GG': raw verification message from GPG for a signed commit
-- '%G?': show "G" for a good (valid) signature,
-  "B" for a bad signature,
-  "U" for a good signature with unknown validity,
-  "X" for a good signature that has expired,
-  "Y" for a good signature made by an expired key,
-  "R" for a good signature made by a revoked key,
-  "E" if the signature cannot be checked (e.g. missing key)
-  and "N" for no signature
-- '%GS': show the name of the signer for a signed commit
-- '%GK': show the key used to sign a signed commit
-- '%GF': show the fingerprint of the key used to sign a signed commit
-- '%GP': show the fingerprint of the primary key whose subkey was used
-  to sign a signed commit
-- '%gD': reflog selector, e.g., `refs/stash@{1}` or
-  `refs/stash@{2 minutes ago`}; the format follows the rules described
-  for the `-g` option. The portion before the `@` is the refname as
-  given on the command line (so `git log -g refs/heads/master` would
-  yield `refs/heads/master@{0}`).
-- '%gd': shortened reflog selector; same as `%gD`, but the refname
-  portion is shortened for human readability (so `refs/heads/master`
-  becomes just `master`).
-- '%gn': reflog identity name
-- '%gN': reflog identity name (respecting .mailmap, see
-  linkgit:git-shortlog[1] or linkgit:git-blame[1])
-- '%ge': reflog identity email
-- '%gE': reflog identity email (respecting .mailmap, see
-  linkgit:git-shortlog[1] or linkgit:git-blame[1])
-- '%gs': reflog subject
-- '%Cred': switch color to red
-- '%Cgreen': switch color to green
-- '%Cblue': switch color to blue
-- '%Creset': reset color
-- '%C(...)': color specification, as described under Values in the
-  "CONFIGURATION FILE" section of linkgit:git-config[1].
-  By default, colors are shown only when enabled for log output (by
-  `color.diff`, `color.ui`, or `--color`, and respecting the `auto`
-  settings of the former if we are going to a terminal). `%C(auto,...)`
-  is accepted as a historical synonym for the default (e.g.,
-  `%C(auto,red)`). Specifying `%C(always,...)` will show the colors
-  even when color is not otherwise enabled (though consider
-  just using `--color=always` to enable color for the whole output,
-  including this format and anything else git might color).  `auto`
-  alone (i.e. `%C(auto)`) will turn on auto coloring on the next
-  placeholders until the color is switched again.
-- '%m': left (`<`), right (`>`) or boundary (`-`) mark
-- '%n': newline
-- '%%': a raw '%'
-- '%x00': print a byte from a hex code
-- '%w([<w>[,<i1>[,<i2>]]])': switch line wrapping, like the -w option of
-  linkgit:git-shortlog[1].
-- '%<(<N>[,trunc|ltrunc|mtrunc])': make the next placeholder take at
-  least N columns, padding spaces on the right if necessary.
-  Optionally truncate at the beginning (ltrunc), the middle (mtrunc)
-  or the end (trunc) if the output is longer than N columns.
-  Note that truncating only works correctly with N >= 2.
-- '%<|(<N>)': make the next placeholder take at least until Nth
-  columns, padding spaces on the right if necessary
-- '%>(<N>)', '%>|(<N>)': similar to '%<(<N>)', '%<|(<N>)'
-  respectively, but padding spaces on the left
-- '%>>(<N>)', '%>>|(<N>)': similar to '%>(<N>)', '%>|(<N>)'
-  respectively, except that if the next placeholder takes more spaces
-  than given and there are spaces on its left, use those spaces
-- '%><(<N>)', '%><|(<N>)': similar to '%<(<N>)', '%<|(<N>)'
-  respectively, but padding both sides (i.e. the text is centered)
-- %(trailers[:options]): display the trailers of the body as interpreted
-  by linkgit:git-interpret-trailers[1]. The `trailers` string may be
-  followed by a colon and zero or more comma-separated options. If the
-  `only` option is given, omit non-trailer lines from the trailer block.
-  If the `unfold` option is given, behave as if interpret-trailer's
-  `--unfold` option was given.  E.g., `%(trailers:only,unfold)` to do
-  both.
+'%GG':: raw verification message from GPG for a signed commit
+'%G?':: show "G" for a good (valid) signature,
+	"B" for a bad signature,
+	"U" for a good signature with unknown validity,
+	"X" for a good signature that has expired,
+	"Y" for a good signature made by an expired key,
+	"R" for a good signature made by a revoked key,
+	"E" if the signature cannot be checked (e.g. missing key)
+	and "N" for no signature
+'%GS':: show the name of the signer for a signed commit
+'%GK':: show the key used to sign a signed commit
+'%GF':: show the fingerprint of the key used to sign a signed commit
+'%GP':: show the fingerprint of the primary key whose subkey was used
+	to sign a signed commit
+'%gD':: reflog selector, e.g., `refs/stash@{1}` or `refs/stash@{2
+	minutes ago`}; the format follows the rules described for the
+	`-g` option. The portion before the `@` is the refname as
+	given on the command line (so `git log -g refs/heads/master`
+	would yield `refs/heads/master@{0}`).
+'%gd':: shortened reflog selector; same as `%gD`, but the refname
+	portion is shortened for human readability (so
+	`refs/heads/master` becomes just `master`).
+'%gn':: reflog identity name
+'%gN':: reflog identity name (respecting .mailmap, see
+	linkgit:git-shortlog[1] or linkgit:git-blame[1])
+'%ge':: reflog identity email
+'%gE':: reflog identity email (respecting .mailmap, see
+	linkgit:git-shortlog[1] or linkgit:git-blame[1])
+'%gs':: reflog subject
+'%(trailers[:options])':: display the trailers of the body as
+			  interpreted by
+			  linkgit:git-interpret-trailers[1]. The
+			  `trailers` string may be followed by a colon
+			  and zero or more comma-separated options:
+** 'key=<K>': only show trailers with specified key. Matching is done
+   case-insensitively and trailing colon is optional. If option is
+   given multiple times trailer lines matching any of the keys are
+   shown. This option automatically enables the `only` option so that
+   non-trailer lines in the trailer block are hidden. If that is not
+   desired it can be disabled with `only=false`.  E.g.,
+   `%(trailers:key=Reviewed-by)` shows trailer lines with key
+   `Reviewed-by`.
+** 'only[=val]': select whether non-trailer lines from the trailer
+   block should be included. The `only` keyword may optionally be
+   followed by an equal sign and one of `true`, `on`, `yes` to omit or
+   `false`, `off`, `no` to show the non-trailer lines. If option is
+   given without value it is enabled. If given multiple times the last
+   value is used.
+** 'separator=<SEP>': specify a separator inserted between trailer
+   lines. When this option is not given each trailer line is
+   terminated with a line feed character. The string SEP may contain
+   the literal formatting codes described above. To use comma as
+   separator one must use `%x2C` as it would otherwise be parsed as
+   next option. If separator option is given multiple times only the
+   last one is used. E.g., `%(trailers:key=Ticket,separator=%x2C )`
+   shows all trailer lines whose key is "Ticket" separated by a comma
+   and a space.
+** 'unfold[=val]': make it behave as if interpret-trailer's `--unfold`
+   option was given. In same way as to for `only` it can be followed
+   by an equal sign and explicit value. E.g.,
+   `%(trailers:only,unfold=true)` unfolds and shows all trailer lines.
+** 'valueonly[=val]': skip over the key part of the trailer line and only
+   show the value part. Also this optionally allows explicit value.
 
 NOTE: Some placeholders may depend on other options given to the
 revision traversal engine. For example, the `%g*` reflog options will
diff --git a/pretty.c b/pretty.c
index 0ab45d10d7..d2995b13ed 100644
--- a/pretty.c
+++ b/pretty.c
@@ -1057,13 +1057,26 @@ static size_t parse_padding_placeholder(struct strbuf *sb,
 	return 0;
 }
 
-static int match_placeholder_arg(const char *to_parse, const char *candidate,
-				 const char **end)
+static int match_placeholder_arg_value(const char *to_parse, const char *candidate,
+				       const char **end, const char **valuestart,
+				       size_t *valuelen)
 {
 	const char *p;
 
 	if (!(skip_prefix(to_parse, candidate, &p)))
 		return 0;
+	if (valuestart) {
+		if (*p == '=') {
+			*valuestart = p + 1;
+			*valuelen = strcspn(*valuestart, ",)");
+			p = *valuestart + *valuelen;
+		} else {
+			if (*p != ',' && *p != ')')
+				return 0;
+			*valuestart = NULL;
+			*valuelen = 0;
+		}
+	}
 	if (*p == ',') {
 		*end = p + 1;
 		return 1;
@@ -1075,6 +1088,47 @@ static int match_placeholder_arg(const char *to_parse, const char *candidate,
 	return 0;
 }
 
+static int match_placeholder_bool_arg(const char *to_parse, const char *candidate,
+				      const char **end, int *val)
+{
+	const char *argval;
+	char *strval;
+	size_t arglen;
+	int v;
+
+	if (!match_placeholder_arg_value(to_parse, candidate, end, &argval, &arglen))
+		return 0;
+
+	if (!argval) {
+		*val = 1;
+		return 1;
+	}
+
+	strval = xstrndup(argval, arglen);
+	v = git_parse_maybe_bool(strval);
+	free(strval);
+
+	if (v == -1)
+		return 0;
+
+	*val = v;
+
+	return 1;
+}
+
+static int format_trailer_match_cb(const struct strbuf *key, void *ud)
+{
+	const struct string_list *list = ud;
+	const struct string_list_item *item;
+
+	for_each_string_list_item (item, list) {
+		if (key->len == (uintptr_t)item->util &&
+		    !strncasecmp(item->string, key->buf, key->len))
+			return 1;
+	}
+	return 0;
+}
+
 static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 				const char *placeholder,
 				void *context)
@@ -1084,10 +1138,14 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 	const char *msg = c->message;
 	struct commit_list *p;
 	const char *arg;
-	int ch;
+	size_t res;
 	char **slot;
 
 	/* these are independent of the commit */
+	res = strbuf_expand_literal_cb(sb, placeholder, NULL);
+	if (res)
+		return res;
+
 	switch (placeholder[0]) {
 	case 'C':
 		if (starts_with(placeholder + 1, "(auto)")) {
@@ -1106,16 +1164,6 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 			 */
 			return ret;
 		}
-	case 'n':		/* newline */
-		strbuf_addch(sb, '\n');
-		return 1;
-	case 'x':
-		/* %x00 == NUL, %x0a == LF, etc. */
-		ch = hex2chr(placeholder + 1);
-		if (ch < 0)
-			return 0;
-		strbuf_addch(sb, ch);
-		return 3;
 	case 'w':
 		if (placeholder[1] == '(') {
 			unsigned long width = 0, indent1 = 0, indent2 = 0;
@@ -1322,24 +1370,53 @@ static size_t format_commit_one(struct strbuf *sb, /* in UTF-8 */
 
 	if (skip_prefix(placeholder, "(trailers", &arg)) {
 		struct process_trailer_options opts = PROCESS_TRAILER_OPTIONS_INIT;
+		struct string_list filter_list = STRING_LIST_INIT_NODUP;
+		struct strbuf sepbuf = STRBUF_INIT;
+		size_t ret = 0;
 
 		opts.no_divider = 1;
 
 		if (*arg == ':') {
 			arg++;
 			for (;;) {
-				if (match_placeholder_arg(arg, "only", &arg))
+				const char *argval;
+				size_t arglen;
+
+				if (match_placeholder_arg_value(arg, "key", &arg, &argval, &arglen)) {
+					uintptr_t len = arglen;
+
+					if (!argval)
+						goto trailer_out;
+
+					if (len && argval[len - 1] == ':')
+						len--;
+					string_list_append(&filter_list, argval)->util = (char *)len;
+
+					opts.filter = format_trailer_match_cb;
+					opts.filter_data = &filter_list;
 					opts.only_trailers = 1;
-				else if (match_placeholder_arg(arg, "unfold", &arg))
-					opts.unfold = 1;
-				else
+				} else if (match_placeholder_arg_value(arg, "separator", &arg, &argval, &arglen)) {
+					char *fmt;
+
+					strbuf_reset(&sepbuf);
+					fmt = xstrndup(argval, arglen);
+					strbuf_expand(&sepbuf, fmt, strbuf_expand_literal_cb, NULL);
+					free(fmt);
+					opts.separator = &sepbuf;
+				} else if (!match_placeholder_bool_arg(arg, "only", &arg, &opts.only_trailers) &&
+					   !match_placeholder_bool_arg(arg, "unfold", &arg, &opts.unfold) &&
+					   !match_placeholder_bool_arg(arg, "valueonly", &arg, &opts.value_only))
 					break;
 			}
 		}
 		if (*arg == ')') {
 			format_trailers_from_commit(sb, msg + c->subject_off, &opts);
-			return arg - placeholder + 1;
+			ret = arg - placeholder + 1;
 		}
+	trailer_out:
+		string_list_clear(&filter_list, 0);
+		strbuf_release(&sepbuf);
+		return ret;
 	}
 
 	return 0;	/* unknown placeholder */
diff --git a/strbuf.c b/strbuf.c
index f6a6cf78b9..78eecd29f7 100644
--- a/strbuf.c
+++ b/strbuf.c
@@ -380,6 +380,27 @@ void strbuf_expand(struct strbuf *sb, const char *format, expand_fn_t fn,
 	}
 }
 
+size_t strbuf_expand_literal_cb(struct strbuf *sb,
+				const char *placeholder,
+				void *context)
+{
+	int ch;
+
+	switch (placeholder[0]) {
+	case 'n':		/* newline */
+		strbuf_addch(sb, '\n');
+		return 1;
+	case 'x':
+		/* %x00 == NUL, %x0a == LF, etc. */
+		ch = hex2chr(placeholder + 1);
+		if (ch < 0)
+			return 0;
+		strbuf_addch(sb, ch);
+		return 3;
+	}
+	return 0;
+}
+
 size_t strbuf_expand_dict_cb(struct strbuf *sb, const char *placeholder,
 		void *context)
 {
diff --git a/strbuf.h b/strbuf.h
index fc40873b65..52e44c9ab8 100644
--- a/strbuf.h
+++ b/strbuf.h
@@ -320,6 +320,14 @@ void strbuf_expand(struct strbuf *sb,
 		   expand_fn_t fn,
 		   void *context);
 
+/**
+ * Used as callback for `strbuf_expand` to only expand literals
+ * (i.e. %n and %xNN). The context argument is ignored.
+ */
+size_t strbuf_expand_literal_cb(struct strbuf *sb,
+				const char *placeholder,
+				void *context);
+
 /**
  * Used as callback for `strbuf_expand()`, expects an array of
  * struct strbuf_expand_dict_entry as context, i.e. pairs of
diff --git a/t/t4205-log-pretty-formats.sh b/t/t4205-log-pretty-formats.sh
index 7df8c3d4ec..f42a69faa2 100755
--- a/t/t4205-log-pretty-formats.sh
+++ b/t/t4205-log-pretty-formats.sh
@@ -578,6 +578,24 @@ test_expect_success '%(trailers:only) shows only "key: value" trailers' '
 	test_cmp expect actual
 '
 
+test_expect_success '%(trailers:only=yes) shows only "key: value" trailers' '
+	git log --no-walk --pretty=format:"%(trailers:only=yes)" >actual &&
+	grep -v patch.description <trailers >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:only=no) shows all trailers' '
+	git log --no-walk --pretty=format:"%(trailers:only=no)" >actual &&
+	cat trailers >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:only=no,only=true) shows only "key: value" trailers' '
+	git log --no-walk --pretty=format:"%(trailers:only=yes)" >actual &&
+	grep -v patch.description <trailers >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success '%(trailers:unfold) unfolds trailers' '
 	git log --no-walk --pretty="%(trailers:unfold)" >actual &&
 	{
@@ -598,6 +616,105 @@ test_expect_success ':only and :unfold work together' '
 	test_cmp expect actual
 '
 
+test_expect_success 'pretty format %(trailers:key=foo) shows that trailer' '
+	git log --no-walk --pretty="format:%(trailers:key=Acked-by)" >actual &&
+	echo "Acked-by: A U Thor <author@example.com>" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers:key=foo) is case insensitive' '
+	git log --no-walk --pretty="format:%(trailers:key=AcKed-bY)" >actual &&
+	echo "Acked-by: A U Thor <author@example.com>" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers:key=foo:) trailing colon also works' '
+	git log --no-walk --pretty="format:%(trailers:key=Acked-by:)" >actual &&
+	echo "Acked-by: A U Thor <author@example.com>" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers:key=foo) multiple keys' '
+	git log --no-walk --pretty="format:%(trailers:key=Acked-by:,key=Signed-off-By)" >actual &&
+	grep -v patch.description <trailers >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:key=nonexistant) becomes empty' '
+	git log --no-walk --pretty="x%(trailers:key=Nacked-by)x" >actual &&
+	echo "xx" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:key=foo) handles multiple lines even if folded' '
+	git log --no-walk --pretty="format:%(trailers:key=Signed-Off-by)" >actual &&
+	grep -v patch.description <trailers | grep -v Acked-by >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:key=foo,unfold) properly unfolds' '
+	git log --no-walk --pretty="format:%(trailers:key=Signed-Off-by,unfold)" >actual &&
+	unfold <trailers | grep Signed-off-by >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers:key=foo,only=no) also includes nontrailer lines' '
+	git log --no-walk --pretty="format:%(trailers:key=Acked-by,only=no)" >actual &&
+	{
+		echo "Acked-by: A U Thor <author@example.com>" &&
+		grep patch.description <trailers
+	} >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:key) without value is error' '
+	git log --no-walk --pretty="tformat:%(trailers:key)" >actual &&
+	echo "%(trailers:key)" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '%(trailers:key=foo,valueonly) shows only value' '
+	git log --no-walk --pretty="format:%(trailers:key=Acked-by,valueonly)" >actual &&
+	echo "A U Thor <author@example.com>" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers:separator) changes separator' '
+	git log --no-walk --pretty=format:"X%(trailers:separator=%x00,unfold)X" >actual &&
+	printf "XSigned-off-by: A U Thor <author@example.com>\0Acked-by: A U Thor <author@example.com>\0[ v2 updated patch description ]\0Signed-off-by: A U Thor <author@example.com>X" >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'pretty format %(trailers) combining separator/key/valueonly' '
+	git commit --allow-empty -F - <<-\EOF &&
+	Important fix
+
+	The fix is explained here
+
+	Closes: #1234
+	EOF
+
+	git commit --allow-empty -F - <<-\EOF &&
+	Another fix
+
+	The fix is explained here
+
+	Closes: #567
+	Closes: #890
+	EOF
+
+	git commit --allow-empty -F - <<-\EOF &&
+	Does not close any tickets
+	EOF
+
+	git log --pretty="%s% (trailers:separator=%x2c%x20,key=Closes,valueonly)" HEAD~3.. >actual &&
+	test_write_lines \
+		"Does not close any tickets" \
+		"Another fix #567, #890" \
+		"Important fix #1234" >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'trailer parsing not fooled by --- line' '
 	git commit --allow-empty -F - <<-\EOF &&
 	this is the subject
diff --git a/trailer.c b/trailer.c
index 0796f326b3..0c414f2fed 100644
--- a/trailer.c
+++ b/trailer.c
@@ -1129,10 +1129,11 @@ static void format_trailer_info(struct strbuf *out,
 				const struct trailer_info *info,
 				const struct process_trailer_options *opts)
 {
+	size_t origlen = out->len;
 	size_t i;
 
 	/* If we want the whole block untouched, we can take the fast path. */
-	if (!opts->only_trailers && !opts->unfold) {
+	if (!opts->only_trailers && !opts->unfold && !opts->filter && !opts->separator) {
 		strbuf_add(out, info->trailer_start,
 			   info->trailer_end - info->trailer_start);
 		return;
@@ -1147,15 +1148,29 @@ static void format_trailer_info(struct strbuf *out,
 			struct strbuf val = STRBUF_INIT;
 
 			parse_trailer(&tok, &val, NULL, trailer, separator_pos);
-			if (opts->unfold)
-				unfold_value(&val);
+			if (!opts->filter || opts->filter(&tok, opts->filter_data)) {
+				if (opts->unfold)
+					unfold_value(&val);
 
-			strbuf_addf(out, "%s: %s\n", tok.buf, val.buf);
+				if (opts->separator && out->len != origlen)
+					strbuf_addbuf(out, opts->separator);
+				if (!opts->value_only)
+					strbuf_addf(out, "%s: ", tok.buf);
+				strbuf_addbuf(out, &val);
+				if (!opts->separator)
+					strbuf_addch(out, '\n');
+			}
 			strbuf_release(&tok);
 			strbuf_release(&val);
 
 		} else if (!opts->only_trailers) {
+			if (opts->separator && out->len != origlen) {
+				strbuf_addbuf(out, opts->separator);
+			}
 			strbuf_addstr(out, trailer);
+			if (opts->separator) {
+				strbuf_rtrim(out);
+			}
 		}
 	}
 
diff --git a/trailer.h b/trailer.h
index b997739649..203acf4ee1 100644
--- a/trailer.h
+++ b/trailer.h
@@ -72,6 +72,10 @@ struct process_trailer_options {
 	int only_input;
 	int unfold;
 	int no_divider;
+	int value_only;
+	const struct strbuf *separator;
+	int (*filter)(const struct strbuf *, void *);
+	void *filter_data;
 };
 
 #define PROCESS_TRAILER_OPTIONS_INIT {0}