[PATCH v3] git-credential-store: skip empty lines and comments from store

["Carlo Marcelo Arenas Belón" <carenas@gmail.com>]

with the added checks for invalid URLs in credentials, any locally
modified store files which might have empty lines or even comments
were reported[1] failing to parse as valid credentials.

using the store file in this manner wasn't intended by the original
code and it had latent issues which the new code dutifully prevented
but since the strings used wouldn't had been valid credentials anyway
we could instead detect them and skip the matching logic and therefore
formalize this "feature".

trim all lines as they are being read from the store file and skip the
ones that will be otherwise empty or that start with "#" (therefore
assuming them to be comments)

[1] https://stackoverflow.com/a/61420852/5005936

Reported-by: Dirk <dirk@ed4u.de>
Helped-by: Eric Sunshine <sunshine@sunshineco.com>
Signed-off-by: Carlo Marcelo Arenas Belón <carenas@gmail.com>
---
v3:
* avoid using q_to_cr as suggested by Peff
* a more verbose commit message and slightly more complete documentation 
v2:
* use a here-doc for clarity as suggested by Eric
* improve commit message and include documentation

 Documentation/git-credential-store.txt |  7 +++++++
 credential-store.c                     |  3 +++
 t/t0302-credential-store.sh            | 15 +++++++++++++++
 3 files changed, 25 insertions(+)

diff --git a/Documentation/git-credential-store.txt b/Documentation/git-credential-store.txt
index 693dd9d9d7..48ab4b13e5 100644
--- a/Documentation/git-credential-store.txt
+++ b/Documentation/git-credential-store.txt
@@ -101,6 +101,13 @@ username (if we already have one) match, then the password is returned
 to Git. See the discussion of configuration in linkgit:gitcredentials[7]
 for more information.
 
+Note that the file used is not a configuration file and should be ideally
+managed only through git, as any manually introduced typos will compromise
+the validation of credentials.
+
+The parser will ignore any lines starting with the '#' character during
+the processing of credentials for read, though.
+
 GIT
 ---
 Part of the linkgit:git[1] suite
diff --git a/credential-store.c b/credential-store.c
index c010497cb2..b2f160890d 100644
--- a/credential-store.c
+++ b/credential-store.c
@@ -24,6 +24,9 @@ static int parse_credential_file(const char *fn,
 	}
 
 	while (strbuf_getline_lf(&line, fh) != EOF) {
+		strbuf_trim(&line);
+		if (line.len == 0 || *line.buf == '#')
+			continue;
 		credential_from_url(&entry, line.buf);
 		if (entry.username && entry.password &&
 		    credential_match(c, &entry)) {
diff --git a/t/t0302-credential-store.sh b/t/t0302-credential-store.sh
index d6b54e8c65..5e6ace3a06 100755
--- a/t/t0302-credential-store.sh
+++ b/t/t0302-credential-store.sh
@@ -120,4 +120,19 @@ test_expect_success 'erase: erase matching credentials from both xdg and home fi
 	test_must_be_empty "$HOME/.config/git/credentials"
 '
 
+test_expect_success 'get: allow for empty lines or comments in store file' '
+	test_write_lines "#comment" " " "" \
+		 https://user:pass@example.com >"$HOME/.git-credentials" &&
+	check fill store <<-\EOF
+	protocol=https
+	host=example.com
+	--
+	protocol=https
+	host=example.com
+	username=user
+	password=pass
+	--
+	EOF
+'
+
 test_done
-- 
2.26.2.569.g1d74ac4d14