[PATCH 2/2] checkout-index: omit entries with no tempname from --temp output

From: Matheus Tavares <matheus.bernardino@usp.br>
Date: Feb 8, 2021, 19:36 UTC
Message-ID: <1275701345b7e198ec83ad4fdcc2dda6d9775ef3.1612812581.git.matheus.bernardino@usp.br>
In-Reply-To: <cover.1612812581.git.matheus.bernardino@usp.br>

With --temp (or --stage=all, which implies --temp), checkout-index writes a list to stdout associating temporary file names to the entries' names. But if it fails to write an entry, and the failure happens before even assigning a temporary filename to that entry, we get an odd output line. This can be seen when trying to check out a symlink whose blob is missing:

$ missing_blob=$(git hash-object --stdin </dev/null)
$ git update-index --add --cacheinfo 120000,$missing_blob,foo
$ git checkout-index --temp foo
error: unable to read sha1 file of foo (e69de29bb2d1d6434b8b29ae775ad8c2e48c5391)
        foo

The 'TAB foo' line is not much useful and it might break scripts that expect the 'tempname TAB foo' output. So let's omit such entries from the stdout list (but leaving the error message on stderr).

We could also consider omitting _all_ failed entries from the output list, but that's probably not a good idea as the associated tempfiles may have been created even when checkout failed, so scripts may want to use the output list for cleanup.

Signed-off-by: Matheus Tavares <matheus.bernardino@usp.br>
---
 builtin/checkout-index.c | 39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/builtin/checkout-index.c b/builtin/checkout-index.c
index 4bbfc92dce..a9f0f0a225 100644
--- a/builtin/checkout-index.c
+++ b/builtin/checkout-index.c
@@ -23,25 +23,38 @@ static struct checkout state = CHECKOUT_INIT;
 static void write_tempfile_record(const char *name, const char *prefix)
 {
 	int i;
+	int have_tempname = 0;
 
 	if (CHECKOUT_ALL == checkout_stage) {
-		for (i = 1; i < 4; i++) {
-			if (i > 1)
-				putchar(' ');
-			if (topath[i][0])
-				fputs(topath[i], stdout);
-			else
-				putchar('.');
+		for (i = 1; i < 4; i++)
+			if (topath[i][0]) {
+				have_tempname = 1;
+				break;
+			}
+
+		if (have_tempname) {
+			for (i = 1; i < 4; i++) {
+				if (i > 1)
+					putchar(' ');
+				if (topath[i][0])
+					fputs(topath[i], stdout);
+				else
+					putchar('.');
+			}
 		}
-	} else
+	} else if (topath[checkout_stage][0]) {
+		have_tempname = 1;
 		fputs(topath[checkout_stage], stdout);
+	}
 
-	putchar('\t');
-	write_name_quoted_relative(name, prefix, stdout,
-				   nul_term_line ? '\0' : '\n');
+	if (have_tempname) {
+		putchar('\t');
+		write_name_quoted_relative(name, prefix, stdout,
+					   nul_term_line ? '\0' : '\n');
 
-	for (i = 0; i < 4; i++) {
-		topath[i][0] = 0;
+		for (i = 0; i < 4; i++) {
+			topath[i][0] = 0;
+		}
 	}
 }

-- 
2.29.2