[PATCH 10/15] for-each-ref: introduce format specifier %>(*) and %<(*)

[Ramkumar Ramachandra <artagnon@gmail.com>]

From: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>

Pretty placeholders %>(N) and %<(N) require a user provided width N,
which makes sense because the commit chain could be really long and the
user only needs to look at a few at the top, going to the end just to
calculate the best width wastes CPU cycles.

for-each-ref is different; the display set is small, and we display them
all at once. We even support sorting, which goes through all display
items anyway.  This patch introduces new %>(*) and %<(*), which are
supposed to be followed immediately by %(fieldname) (i.e. original
for-each-ref specifiers, not ones coming from pretty.c). They calculate
the best width for the %(fieldname), ignoring ansi escape sequences if
any.

[rr: documentation]

Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Signed-off-by: Ramkumar Ramachandra <artagnon@gmail.com>
---
 Documentation/git-for-each-ref.txt |  7 +++++++
 builtin/for-each-ref.c             | 38 ++++++++++++++++++++++++++++++++++++++
 t/t6300-for-each-ref.sh            | 20 ++++++++++++++++++++
 3 files changed, 65 insertions(+)

diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index d8ad758..8cbc08c 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -47,6 +47,10 @@ OPTIONS
 	are hex digits interpolates to character with hex code
 	`xx`; for example `%00` interpolates to `\0` (NUL),
 	`%09` to `\t` (TAB) and `%0a` to `\n` (LF).
++
+Placeholders `%<(*)` and `%>(*)` work like `%<(<N>)` and `%>(<N>)`
+respectively, except that the width of the next placeholder is
+calculated.
 
 <pretty>::
 	A format string with supporting placeholders described in the
@@ -68,6 +72,9 @@ Caveats:
 3. Only the placeholders inherited from `<format>` will respect
    quoting settings.
 
+3. Only the placeholders inherited from `<format>` will work with the
+   alignment placeholders `%<(*)` and '%>(*)`.
+
 <pattern>...::
 	If one or more patterns are given, only refs are shown that
 	match against at least one pattern, either using fnmatch(3) or
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 39454fb..da479d1 100644
--- a/builtin/for-each-ref.c
+++ b/builtin/for-each-ref.c
@@ -9,6 +9,7 @@
 #include "quote.h"
 #include "parse-options.h"
 #include "remote.h"
+#include "utf8.h"
 
 /* Quoting styles */
 #define QUOTE_NONE 0
@@ -966,10 +967,30 @@ static void show_refs(struct refinfo **refs, int maxcount,
 }
 
 struct format_one_atom_context {
+	struct refinfo **refs;
+	int maxcount;
+
 	struct refinfo *info;
 	int quote_style;
 };
 
+static unsigned int get_atom_width(struct format_one_atom_context *ctx,
+				   const char *start, const char *end)
+{
+	struct strbuf sb = STRBUF_INIT;
+	int i, atom = parse_atom(start, end);
+	unsigned int len = 0, sb_len;
+	for (i = 0; i < ctx->maxcount; i++) {
+		print_value(&sb, ctx->refs[i], atom, ctx->quote_style);
+		sb_len = utf8_strnwidth(sb.buf, sb.len, 1);
+		if (sb_len > len)
+			len = sb_len;
+		strbuf_reset(&sb);
+	}
+	strbuf_release(&sb);
+	return len;
+}
+
 static size_t format_one_atom(struct strbuf *sb, const char *placeholder,
 			      void *format_context, void *user_data,
 			      struct strbuf *subst)
@@ -982,6 +1003,21 @@ static size_t format_one_atom(struct strbuf *sb, const char *placeholder,
 		return 1;
 	}
 
+	/*
+	 * Substitute %>(*)%(atom) and friends with real width.
+	 */
+	if (*placeholder == '>' || *placeholder == '<') {
+		const char *star = placeholder + 1;
+		if (!prefixcmp(star, "(*)%(") &&
+		    ((ep = strchr(star + strlen("(*)%("), ')')) != NULL)) {
+			star++;
+			strbuf_addf(subst, "%c(%u)",
+				    *placeholder,
+				    get_atom_width(ctx, star + strlen("*)%("), ep));
+			return 1 + strlen("(*)");
+		}
+	}
+
 	if (*placeholder != '(')
 		return 0;
 
@@ -1008,6 +1044,8 @@ static void show_pretty_refs(struct refinfo **refs, int maxcount,
 	ctx.abbrev = DEFAULT_ABBREV;
 	ctx.format = format_one_atom;
 	ctx.user_data = &fctx;
+	fctx.refs = refs;
+	fctx.maxcount = maxcount;
 	fctx.quote_style = quote_style;
 	for (i = 0; i < maxcount; i++) {
 		struct commit *commit = NULL;
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index d39e0b4..160018c 100755
--- a/t/t6300-for-each-ref.sh
+++ b/t/t6300-for-each-ref.sh
@@ -196,6 +196,26 @@ test_pretty head '%<(20)%(committername) end' 'C O Mitter           end'
 test_pretty head '%>(20)%(committername) end' '          C O Mitter end'
 test_pretty head '%><(20)%(committername) end' '     C O Mitter      end'
 
+test_expect_success '%<(*)%(refname) A' '
+	git for-each-ref --pretty="%<(*)%(refname) A" >actual &&
+	cat >expected <<EOF &&
+refs/heads/master          A
+refs/remotes/origin/master A
+refs/tags/testtag          A
+EOF
+	test_cmp expected actual
+'
+
+test_expect_success '%>(*)%(refname) A' '
+	git for-each-ref --pretty="%>(*)%(refname) A" >actual &&
+	qz_to_tab_space >expected <<EOF &&
+Z        refs/heads/master A
+refs/remotes/origin/master A
+Z        refs/tags/testtag A
+EOF
+	test_cmp expected actual
+'
+
 test_pretty tag '%(refname)' refs/tags/testtag
 test_pretty tag '%(upstream)' ''
 test_pretty tag '%(objecttype)' tag
-- 
1.8.3.2.736.g869de25