Improve ref validity checking in fetchGit

The previous regex was too strict and did not match what git was allowing. It
could lead to `fetchGit` not accepting valid branch names, even though they
exist in a repository (for example, branch names containing `/`, which are
pretty standard, like `release/1.0` branches).

The new regex defines what a branch name should **NOT** contain. It takes the
definitions from `refs.c` in https://github.com/git/git and `git help
check-ref-format` pages.

This change also introduces a test for ref name validity checking, which
compares the result from Nix with the result of `git check-ref-format --branch`.

1 files changed, 1 insertions, 0 deletions

diff --git a/src/libutil/url.cc b/src/libutil/url.cc
index 5d5328e5d..88c09eef9 100644
--- a/src/libutil/url.cc
+++ b/src/libutil/url.cc
@@ -4,6 +4,7 @@
 namespace nix {
 
 std::regex refRegex(refRegexS, std::regex::ECMAScript);
+std::regex badGitRefRegex(badGitRefRegexS, std::regex::ECMAScript);
 std::regex revRegex(revRegexS, std::regex::ECMAScript);
 std::regex flakeIdRegex(flakeIdRegexS, std::regex::ECMAScript);