[PATCH v2 2/2] branch, for-each-ref: add option to omit empty lines

["Øystein Walle" <oystwa@gmail.com>]

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

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

Signed-off-by: Øystein Walle <oystwa@gmail.com>
---
 Documentation/git-branch.txt       |  4 ++++
 Documentation/git-for-each-ref.txt |  4 ++++
 builtin/branch.c                   |  6 +++++-
 builtin/for-each-ref.c             |  7 +++++--
 t/t3203-branch-output.sh           | 24 ++++++++++++++++++++++++
 t/t6300-for-each-ref.sh            |  8 ++++++++
 6 files changed, 50 insertions(+), 3 deletions(-)

diff --git a/Documentation/git-branch.txt b/Documentation/git-branch.txt
index d382ac69f7..d207da9101 100644
--- a/Documentation/git-branch.txt
+++ b/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
diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index 6da899c629..af790bfa4e 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/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
 -----------
 
diff --git a/builtin/branch.c b/builtin/branch.c
index f63fd45edb..b47fef51fb 100644
--- a/builtin/branch.c
+++ b/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")),
diff --git a/builtin/for-each-ref.c b/builtin/for-each-ref.c
index 6f62f40d12..1fc5130481 100644
--- a/builtin/for-each-ref.c
+++ b/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);
diff --git a/t/t3203-branch-output.sh b/t/t3203-branch-output.sh
index d34d77f893..c06906d83e 100755
--- a/t/t3203-branch-output.sh
+++ b/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>
diff --git a/t/t6300-for-each-ref.sh b/t/t6300-for-each-ref.sh
index c466fd989f..d4ccc22d99 100755
--- a/t/t6300-for-each-ref.sh
+++ b/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 &&
-- 
2.20.1