branch, for-each-ref, tag: add option to omit empty lines

If the given format string expands to the empty string, a newline is
still printed. This makes using the output linewise more tedious. For
example, git update-ref --stdin does not accept empty lines.

Add options to "git branch", "git for-each-ref", and "git tag" to
not print these empty lines.  The default behavior remains the same.

Signed-off-by: Øystein Walle <oystwa@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-branch.txt

@@ -156,6 +156,10 @@ in another worktree linked to the same repository.
 --ignore-case::
 	Sorting and filtering branches are case insensitive.
 
+--omit-empty::
+	Do not print a newline after formatted refs where the format expands
+	to the empty string.
+
 --column[=<options>]::
 --no-column::
 	Display branch listing in columns. See configuration variable

Documentation/git-for-each-ref.txt

@@ -93,6 +93,10 @@ OPTIONS
 --ignore-case::
 	Sorting and filtering refs are case insensitive.
 
+--omit-empty::
+	Do not print a newline after formatted refs where the format expands
+	to the empty string.
+
 FIELD NAMES
 -----------
 

Documentation/git-tag.txt

@@ -131,6 +131,10 @@ options for details.
 --ignore-case::
 	Sorting and filtering tags are case insensitive.
 
+--omit-empty::
+	Do not print a newline after formatted refs where the format expands
+	to the empty string.
+
 --column[=<options>]::
 --no-column::
 	Display tag listing in columns. See configuration variable

builtin/branch.c

@@ -41,6 +41,7 @@ static const char *head;
 static struct object_id head_oid;
 static int recurse_submodules = 0;
 static int submodule_propagate_branches = 0;
+static int omit_empty = 0;
 
 static int branch_use_color = -1;
 static char branch_colors[][COLOR_MAXLEN] = {
@@ -461,7 +462,8 @@ static void print_ref_list(struct ref_filter *filter, struct ref_sorting *sortin
 			string_list_append(output, out.buf);
 		} else {
 			fwrite(out.buf, 1, out.len, stdout);
-			putchar('\n');
+			if (out.len || !omit_empty)
+				putchar('\n');
 		}
 	}
 
@@ -670,6 +672,8 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		OPT_BIT('D', NULL, &delete, N_("delete branch (even if not merged)"), 2),
 		OPT_BIT('m', "move", &rename, N_("move/rename a branch and its reflog"), 1),
 		OPT_BIT('M', NULL, &rename, N_("move/rename a branch, even if target exists"), 2),
+		OPT_BOOL(0, "omit-empty",  &omit_empty,
+			N_("do not output a newline after empty formatted refs")),
 		OPT_BIT('c', "copy", &copy, N_("copy a branch and its reflog"), 1),
 		OPT_BIT('C', NULL, &copy, N_("copy a branch, even if target exists"), 2),
 		OPT_BOOL('l', "list", &list, N_("list branch names")),

builtin/for-each-ref.c

@@ -19,7 +19,7 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 	int i;
 	struct ref_sorting *sorting;
 	struct string_list sorting_options = STRING_LIST_INIT_DUP;
-	int maxcount = 0, icase = 0;
+	int maxcount = 0, icase = 0, omit_empty = 0;
 	struct ref_array array;
 	struct ref_filter filter;
 	struct ref_format format = REF_FORMAT_INIT;
@@ -35,6 +35,8 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 			N_("quote placeholders suitably for python"), QUOTE_PYTHON),
 		OPT_BIT(0 , "tcl",  &format.quote_style,
 			N_("quote placeholders suitably for Tcl"), QUOTE_TCL),
+		OPT_BOOL(0, "omit-empty",  &omit_empty,
+			N_("do not output a newline after empty formatted refs")),
 
 		OPT_GROUP(""),
 		OPT_INTEGER( 0 , "count", &maxcount, N_("show only <n> matched refs")),
@@ -88,7 +90,8 @@ int cmd_for_each_ref(int argc, const char **argv, const char *prefix)
 		if (format_ref_array_item(array.items[i], &format, &output, &err))
 			die("%s", err.buf);
 		fwrite(output.buf, 1, output.len, stdout);
-		putchar('\n');
+		if (output.len || !omit_empty)
+			putchar('\n');
 	}
 
 	strbuf_release(&err);

builtin/tag.c

@@ -37,6 +37,7 @@ static const char * const git_tag_usage[] = {
 static unsigned int colopts;
 static int force_sign_annotate;
 static int config_sign_tag = -1; /* unspecified */
+static int omit_empty = 0;
 
 static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting,
 		     struct ref_format *format)
@@ -74,7 +75,8 @@ static int list_tags(struct ref_filter *filter, struct ref_sorting *sorting,
 		if (format_ref_array_item(array.items[i], format, &output, &err))
 			die("%s", err.buf);
 		fwrite(output.buf, 1, output.len, stdout);
-		putchar('\n');
+		if (output.len || !omit_empty)
+			putchar('\n');
 	}
 
 	strbuf_release(&err);
@@ -473,6 +475,8 @@ int cmd_tag(int argc, const char **argv, const char *prefix)
 		OPT_WITHOUT(&filter.no_commit, N_("print only tags that don't contain the commit")),
 		OPT_MERGED(&filter, N_("print only tags that are merged")),
 		OPT_NO_MERGED(&filter, N_("print only tags that are not merged")),
+		OPT_BOOL(0, "omit-empty",  &omit_empty,
+			N_("do not output a newline after empty formatted refs")),
 		OPT_REF_SORT(&sorting_options),
 		{
 			OPTION_CALLBACK, 0, "points-at", &filter.points_at, N_("object"),

t/t3203-branch-output.sh

@@ -341,6 +341,30 @@ test_expect_success 'git branch with --format=%(rest) must fail' '
 	test_must_fail git branch --format="%(rest)" >actual
 '
 
+test_expect_success 'git branch --format --omit-empty' '
+	cat >expect <<-\EOF &&
+	Refname is (HEAD detached from fromtag)
+	Refname is refs/heads/ambiguous
+	Refname is refs/heads/branch-one
+	Refname is refs/heads/branch-two
+
+	Refname is refs/heads/ref-to-branch
+	Refname is refs/heads/ref-to-remote
+	EOF
+	git branch --format="%(if:notequals=refs/heads/main)%(refname)%(then)Refname is %(refname)%(end)" >actual &&
+	test_cmp expect actual &&
+	cat >expect <<-\EOF &&
+	Refname is (HEAD detached from fromtag)
+	Refname is refs/heads/ambiguous
+	Refname is refs/heads/branch-one
+	Refname is refs/heads/branch-two
+	Refname is refs/heads/ref-to-branch
+	Refname is refs/heads/ref-to-remote
+	EOF
+	git branch --omit-empty --format="%(if:notequals=refs/heads/main)%(refname)%(then)Refname is %(refname)%(end)" >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'worktree colors correct' '
 	cat >expect <<-EOF &&
 	* <GREEN>(HEAD detached from fromtag)<RESET>

t/t6300-for-each-ref.sh

@@ -1374,6 +1374,14 @@ test_expect_success 'for-each-ref --ignore-case ignores case' '
 	test_cmp expect actual
 '
 
+test_expect_success 'for-each-ref --omit-empty works' '
+	git for-each-ref --format="%(refname)" >actual &&
+	test_line_count -gt 1 actual &&
+	git for-each-ref --format="%(if:equals=refs/heads/main)%(refname)%(then)%(refname)%(end)" --omit-empty >actual &&
+	echo refs/heads/main >expect &&
+	test_cmp expect actual
+'
+
 test_expect_success 'for-each-ref --ignore-case works on multiple sort keys' '
 	# name refs numerically to avoid case-insensitive filesystem conflicts
 	nr=0 &&

t/t7004-tag.sh

@@ -2001,6 +2001,22 @@ test_expect_success '--format should list tags as per format given' '
 	test_cmp expect actual
 '
 
+test_expect_success '--format --omit-empty works' '
+	cat >expect <<-\EOF &&
+	refname : refs/tags/v1.0
+
+	refname : refs/tags/v1.1.3
+	EOF
+	git tag -l --format="%(if:notequals=refs/tags/v1.0.1)%(refname)%(then)refname : %(refname)%(end)" "v1*" >actual &&
+	test_cmp expect actual &&
+	cat >expect <<-\EOF &&
+	refname : refs/tags/v1.0
+	refname : refs/tags/v1.1.3
+	EOF
+	git tag -l --omit-empty --format="%(if:notequals=refs/tags/v1.0.1)%(refname)%(then)refname : %(refname)%(end)" "v1*" >actual &&
+	test_cmp expect actual
+'
+
 test_expect_success 'git tag -l with --format="%(rest)" must fail' '
 	test_must_fail git tag -l --format="%(rest)" "v1*"
 '