[PATCH 05/16] index-info.c: identify empty input lines in read_index_info

["Victoria Dye via GitGitGadget" <gitgitgadget@gmail.com>]

From: Victoria Dye <vdye@github.com>

Update 'read_index_info()' to return INDEX_INFO_EMPTY_LINE (value 1), rather
than the default error code (value -1) when the function encounters an empty
line in stdin. This grants the caller the flexibility to handle such
scenarios differently than a typical error. In the case of 'update-index',
we'll still exit with a "malformed input line" error. However, when
'read_index_info()' is used to process the input to 'mktree' in a later
patch, the empty line return value will signal a new tree in --batch mode.

Signed-off-by: Victoria Dye <vdye@github.com>
---
 builtin/update-index.c | 4 +++-
 index-info.c           | 5 +++++
 index-info.h           | 2 ++
 3 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/builtin/update-index.c b/builtin/update-index.c
index 77df380cb54..b1b334807f8 100644
--- a/builtin/update-index.c
+++ b/builtin/update-index.c
@@ -788,7 +788,9 @@ static enum parse_opt_result stdin_cacheinfo_callback(
 		return error("option '%s' must be the last argument", opt->long_name);
 	allow_add = allow_replace = allow_remove = 1;
 	ret = read_index_info(*nul_term_line, apply_index_info, NULL);
-	if (ret)
+	if (ret == INDEX_INFO_EMPTY_LINE)
+		return error("malformed input line ''");
+	else if (ret < 0)
 		return -1;
 
 	return 0;
diff --git a/index-info.c b/index-info.c
index 0b68e34c361..735cbf1f476 100644
--- a/index-info.c
+++ b/index-info.c
@@ -22,6 +22,11 @@ int read_index_info(int nul_term_line, each_index_info_fn fn, void *cbdata)
 		unsigned long ul;
 		int stage;
 
+		if (!buf.len) {
+			ret = INDEX_INFO_EMPTY_LINE;
+			break;
+		}
+
 		/* This reads lines formatted in one of three formats:
 		 *
 		 * (1) mode         SP sha1          TAB path
diff --git a/index-info.h b/index-info.h
index d650498325a..1884972021d 100644
--- a/index-info.h
+++ b/index-info.h
@@ -5,6 +5,8 @@
 
 typedef int (*each_index_info_fn)(unsigned int, struct object_id *, int, const char *, void *);
 
+#define INDEX_INFO_EMPTY_LINE 1
+
 /* Iterate over parsed index info from stdin */
 int read_index_info(int nul_term_line, each_index_info_fn fn, void *cbdata);
 
-- 
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