Resolve reference for remote repository

Resolves the HEAD reference from the remote repository instead
of assuming "master".
This commit is contained in:
Kjetil Orbekk 2021-03-02 20:13:20 -05:00
parent 4bb111c8d4
commit 401e60f289
2 changed files with 106 additions and 7 deletions

View file

@ -5,9 +5,11 @@
#include "store-api.hh" #include "store-api.hh"
#include "url-parts.hh" #include "url-parts.hh"
#include "pathlocks.hh" #include "pathlocks.hh"
#include "util.hh"
#include "fetch-settings.hh" #include "fetch-settings.hh"
#include <regex>
#include <sys/time.h> #include <sys/time.h>
#include <sys/wait.h> #include <sys/wait.h>
@ -19,7 +21,7 @@ namespace nix::fetchers {
// The value itself does not matter, since we always fetch a specific revision or branch. // The value itself does not matter, since we always fetch a specific revision or branch.
// It is set with `-c init.defaultBranch=` instead of `--initial-branch=` to stay compatible with // It is set with `-c init.defaultBranch=` instead of `--initial-branch=` to stay compatible with
// old version of git, which will ignore unrecognized `-c` options. // old version of git, which will ignore unrecognized `-c` options.
const std::string gitInitialBranch = "__nix_dummy_branch"; static const std::string gitInitialBranch = "__nix_dummy_branch";
static std::string getGitDir() static std::string getGitDir()
{ {
@ -30,9 +32,92 @@ static std::string getGitDir()
return *gitDir; return *gitDir;
} }
static std::string readHead(const Path & path) static bool isCacheFileWithinTtl(const time_t now, const struct stat& st) {
return st.st_mtime + settings.tarballTtl > now;
}
static Path getCachePath(std::string key) {
return getCacheDir() + "/nix/gitv3/" +
hashString(htSHA256, key).to_string(Base32, false);
}
// Returns the name of the HEAD branch.
//
// Returns the head branch name as reported by git ls-remote --symref, e.g., if
// ls-remote returns the output below, "main" is returned based on the ref line.
//
// ref: refs/heads/main HEAD
// ...
static std::optional<std::string> readHead(const Path & path)
{ {
return chomp(runProgram("git", true, { "-C", path, "--git-dir", ".git", "rev-parse", "--abbrev-ref", "HEAD" })); auto [exit_code, output] = runProgram(RunOptions {
.program = "git",
.args = {"ls-remote", "--symref", path},
});
if (exit_code != 0) {
return std::nullopt;
}
// Matches the common case when HEAD points to a branch, e.g.:
// "ref: refs/heads/main HEAD".
const static std::regex head_ref_regex("^ref:\\s*([^\\s]+)\\s*HEAD$");
// Matches when HEAD points directly at a commit, e.g.:
// "71abcd... HEAD".
const static std::regex head_rev_regex("^([^\\s]+)\\s*HEAD$");
for (const auto & line : tokenizeString<std::vector<std::string>>(output, "\n")) {
std::smatch match;
if (std::regex_match(line, match, head_ref_regex)) {
debug("resolved HEAD ref '%s' for repo '%s'", match[1], path);
return match[1];
} else if (std::regex_match(line, match, head_rev_regex)) {
debug("resolved HEAD ref '%s' for repo '%s'", match[1], path);
return match[1];
}
}
return std::nullopt;
}
static std::optional<std::string> readHeadCached(std::string actualUrl)
{
// Create a cache path to store the branch of the HEAD ref. Append something
// in front of the URL to prevent collision with the repository itself.
Path cachePath = getCachePath("<ref>|" + actualUrl);
time_t now = time(0);
struct stat st;
std::optional<std::string> cachedRef;
if (stat(cachePath.c_str(), &st) == 0 &&
// The file may be empty, because writeFile() is not atomic.
st.st_size > 0) {
// The cached ref is persisted unconditionally (see below).
cachedRef = readFile(cachePath);
if (isCacheFileWithinTtl(now, st)) {
debug("using cached HEAD ref '%s' for repo '%s'", *cachedRef, actualUrl);
return cachedRef;
}
}
auto ref = readHead(actualUrl);
if (ref) {
debug("storing cached HEAD ref '%s' for repo '%s' at '%s'", *ref, actualUrl, cachePath);
createDirs(dirOf(cachePath));
writeFile(cachePath, *ref);
return ref;
}
if (cachedRef) {
// If the cached git ref is expired in fetch() below, and the 'git fetch'
// fails, it falls back to continuing with the most recent version.
// This function must behave the same way, so we return the expired
// cached ref here.
warn("could not get HEAD ref for repository '%s'; using expired cached ref '%s'", actualUrl, *cachedRef);
return *cachedRef;
}
return std::nullopt;
} }
static bool isNotDotGitDirectory(const Path & path) static bool isNotDotGitDirectory(const Path & path)
@ -331,7 +416,14 @@ struct GitInputScheme : InputScheme
} }
} }
if (!input.getRef()) input.attrs.insert_or_assign("ref", isLocal ? readHead(actualUrl) : "master"); if (!input.getRef()) {
auto head = isLocal ? readHead(actualUrl) : readHeadCached(actualUrl);
if (!head) {
warn("could not read HEAD ref from repo at '%s', using 'master'", actualUrl);
head = "master";
}
input.attrs.insert_or_assign("ref", *head);
}
Attrs unlockedAttrs({ Attrs unlockedAttrs({
{"type", cacheType}, {"type", cacheType},
@ -360,7 +452,7 @@ struct GitInputScheme : InputScheme
} }
} }
Path cacheDir = getCacheDir() + "/nix/gitv3/" + hashString(htSHA256, actualUrl).to_string(Base32, false); Path cacheDir = getCachePath(actualUrl);
repoDir = cacheDir; repoDir = cacheDir;
gitDir = "."; gitDir = ".";
@ -400,7 +492,7 @@ struct GitInputScheme : InputScheme
git fetch to update the local ref to the remote ref. */ git fetch to update the local ref to the remote ref. */
struct stat st; struct stat st;
doFetch = stat(localRefFile.c_str(), &st) != 0 || doFetch = stat(localRefFile.c_str(), &st) != 0 ||
(uint64_t) st.st_mtime + settings.tarballTtl <= (uint64_t) now; !isCacheFileWithinTtl(now, st);
} }
} }

View file

@ -31,7 +31,14 @@ flakeFollowsE=$TEST_ROOT/follows/flakeA/flakeE
for repo in $flake1Dir $flake2Dir $flake3Dir $flake7Dir $templatesDir $nonFlakeDir $flakeA $flakeB $flakeFollowsA; do for repo in $flake1Dir $flake2Dir $flake3Dir $flake7Dir $templatesDir $nonFlakeDir $flakeA $flakeB $flakeFollowsA; do
rm -rf $repo $repo.tmp rm -rf $repo $repo.tmp
mkdir -p $repo mkdir -p $repo
git -C $repo init
# Give one repo a non-master initial branch.
extraArgs=
if [[ $repo == $flake2Dir ]]; then
extraArgs="--initial-branch=main"
fi
git -C $repo init $extraArgs
git -C $repo config user.email "foobar@example.com" git -C $repo config user.email "foobar@example.com"
git -C $repo config user.name "Foobar" git -C $repo config user.name "Foobar"
done done