[bugfix] Do not create an empty dir when git clone fails

git clone is creating a destination empty directory before even
attempting to clone the remote URL. It means that if the user-supplied
remote URL happen to be invalid, an empty directory is getting created
at dest, preventing us to try cloning the same repository once again.

We fixed that issue by checking whether the remote git repository
exists using git ls-remote **before** calling git clone.

git ls-remote will fail on a git repository not containing any git
commit. We add a function to the test bed creating a git repo with one
commit. It's a bit hacky, but that's the best setup I could come with.
We embed a dummy git repo to the my-repo-pins codebase and copy it
during the test phase to a tmp workspace.

Makefile

@@ -5,7 +5,7 @@
 EMACS ?= emacs
 
 # A space-separated list of required package names
-NEEDED_PACKAGES = package-lint seq inheritenv
+NEEDED_PACKAGES = package-lint seq inheritenv ert-async
 
 INIT_PACKAGES="(progn \
   (require 'package) \

my-repo-pins-tests.el

@@ -27,6 +27,7 @@
 ;;; Code:
 
 (require 'ert)
+(require 'ert-async)
 (require 'my-repo-pins)
 
 ;; Test Helpers
@@ -39,13 +40,14 @@ FUNC gets called with the temp dir as parameter.
 The directory gets deleted once we exit FUNC."
   (let ((temp-dir (make-temp-file "my-repo-pins-test-" t)))
     (unwind-protect
-          (funcall func (file-name-as-directory temp-dir))
+        (funcall func (file-name-as-directory temp-dir))
       (delete-directory temp-dir t))))
 
 (defun my-repo-pins--tests-init-fake-git-repo (dir)
   "Create a dummy git repo at DIR.
-
-If DIR doesn't exists, we create it first."
+If DIR doesn't exists, we create it first.
+The created git repository won't contain any tracked file nor
+commits."
   (let* ((d (file-name-as-directory dir))
          (git-process
           (progn
@@ -60,6 +62,24 @@ If DIR doesn't exists, we create it first."
       ;; before moving on.
       (while (accept-process-output git-process)))))
 
+(defun my-repo-pins--tests-init-fake-git-repo-with-commit (dir)
+  "Create a dummy git repo having a valid commit at DIR.
+If DIR doesn't exists, we create it first.
+This function is functionally similar to
+‘my-repo-pins--tests-init-fake-git-repo’, however it's more expensive
+to execute. Only use it when you need a git repository containing some
+commits."
+  (let* ((d (file-name-as-directory dir))
+         (dummy-git-repo "./tests/fixtures/dummy-git-repo"))
+    (unless (file-directory-p d) (make-directory d t))
+    ;; This is a nasty trick. We can't easily generate a git commit on
+    ;; runtime. We also can't check-in a git repository in a git
+    ;; repository.
+    ;; We rename the .git subfolder in the fixture to .git-to-rename
+    ;; to trick git into thinking this is not a git repo.
+    (copy-directory dummy-git-repo d nil nil t)
+    (rename-file (concat d "/.git-to-rename") (concat d "/.git"))))
+
 ;; Test Dirs Setup
 ;;;;;;;;;;;;;;;;;
 
@@ -271,7 +291,49 @@ For reference: a empty test root looks like this:
       ((results (my-repo-pins--get-code-root-projects "/does/not/exist" 3)))
     (should (seq-empty-p results))))
 
+;; Clone Tests
+;;;;;;;;;;;;;;
 
+(ert-deftest-async my-repo-pins--test-git-clone-in-dir-valid-url (done)
+  "Test the ‘my-repo-pins--git-clone-in-dir’ function on a valid repository URL.
+
+Note: this function is async, we can't use
+my--repo-pins--tests-with-temp-dir to create the temporary directory:
+it'll get deleted before the end of the test."
+  (let* ((tmpdir (make-temp-file "my-repo-pins-test-" t))
+         (source (concat tmpdir "/source"))
+         (destination (concat tmpdir "/destination")))
+    (make-directory source)
+    (my-repo-pins--tests-init-fake-git-repo-with-commit source)
+    (my-repo-pins--git-clone-in-dir
+     (concat "file://" source)
+     destination
+     (lambda (exit-code)
+       (message "tmpdir: %s" tmpdir)
+       (should (eq exit-code 0))
+       (should (file-exists-p (concat tmpdir "/destination/hello")))
+       (delete-directory tmpdir t)
+       (funcall done)))))
+
+(ert-deftest-async my-repo-pins--test-git-clone-in-dir-invalid-url (done)
+  "Test the ‘my-repo-pins--git-clone-in-dir’ function on a valid repository URL.
+
+Note: this function is async, we can't use
+my--repo-pins--tests-with-temp-dir to create the temporary directory:
+it'll get deleted before the end of the test."
+  (let* ((tmpdir (make-temp-file "my-repo-pins-test-" t))
+         (source (concat tmpdir "/source"))
+         (destination (concat tmpdir "/destination")))
+    (make-directory source)
+    (my-repo-pins--tests-init-fake-git-repo-with-commit source)
+    (my-repo-pins--git-clone-in-dir
+     (concat "file://" source "doesnotexists")
+     destination
+     (lambda (exit-code)
+       (should (not (eq exit-code 0)))
+       (should (not (file-exists-p (concat tmpdir "/destination"))))
+       (delete-directory tmpdir t)
+       (funcall done)))))
 ;; Test Fetchers
 ;;;;;;;;;;;;;;;;;
 
@@ -340,20 +402,6 @@ For reference: a empty test root looks like this:
   (should (equal (my-repo-pins--filepath-from-clone-url "git@github.com:NinjaTrappeur/my-repo-pins.el.git") "github.com/NinjaTrappeur/my-repo-pins.el"))
   (should (equal (my-repo-pins--filepath-from-clone-url "git@github.com:NinjaTrappeur/my-repo-pins.el") "github.com/NinjaTrappeur/my-repo-pins.el")))
 
-(ert-deftest my-repo-pins--test-git-clone-in-dir ()
-  "Test the my-repo-pins--git-clone-in-dir function."
-    (my-repo-pins--tests-run-on-testroot-1
-     (lambda (dir)
-       (let*
-           ((tmpdir (make-temp-file "my-repo-pins-test-" t))
-            (git-process (my-repo-pins--git-clone-in-dir
-                          (format "file://%s" (concat dir "example1.tld/user1/proj1/"))
-                          tmpdir)))
-         (progn
-           (while (accept-process-output git-process))
-           (should (file-exists-p (format "%s/.git" tmpdir)))
-           (delete-directory tmpdir t))))))
-
 ;;; State Management tests
 
 (ert-deftest my-repo-pins--test-init-forges-state ()

my-repo-pins.el

@@ -142,8 +142,22 @@ Returns the git PROCESS object."
 (defun my-repo-pins--git-clone-in-dir (clone-url checkout-filepath &optional callback)
   "Clone the CLONE-URL repo at CHECKOUT-FILEPATH.
 
+Call CALLBACK with the git exit code once the git subprocess exits.
+Checks first whether or not CLONE-URL is valid using
+‘my-repo-pins--git-ls-remote-in-dir’ to prevent git clone from
+creating an empty directory at CHECKOUT-FILEPATH."
+  (my-repo-pins--git-ls-remote-in-dir
+   clone-url
+   (lambda (exit-code)
+     (if (eq exit-code 0)
+         (my-repo-pins--call-git-in-dir "~/" callback "clone" clone-url checkout-filepath)
+       (funcall callback exit-code)))))
+
+(defun my-repo-pins--git-ls-remote-in-dir (clone-url &optional callback)
+  "Check if a CLONE-URL is valid using git ls-remote.
+
 Call CALLBACK with no arguments once the git subprocess exists."
-  (my-repo-pins--call-git-in-dir "~/" callback "clone" clone-url checkout-filepath))
+  (my-repo-pins--call-git-in-dir "~/" callback "ls-remote" "-q" "--exit-code" clone-url))
 
 ;;===========================
 ;; Internal: builtin fetchers
@@ -722,6 +736,25 @@ url."
                         (find-file dest-dir)))))))
         (clone-ssh))))
 
+(defun my-repo-pins--clone-from-full-url (full-url &optional callback)
+  "Clone a repository from a fully-qualified FULL-URL git URL.
+
+CALLBACK is called once the git process exited. It takes a single
+exit-code parameter containing the process exit code."
+  (let*
+      ((code-root (my-repo-pins--safe-get-code-root))
+       (dest-dir (concat code-root (my-repo-pins--filepath-from-clone-url full-url))))
+    (if (not (file-directory-p dest-dir))
+        (my-repo-pins--git-clone-in-dir
+         full-url
+         dest-dir
+         (lambda (exit-code)
+           (if callback
+               (funcall callback exit-code))
+           (if (equal exit-code 0)
+               (find-file dest-dir)
+             (error "Cannot clone %s" full-url))))
+      (error "%s does not seem to be a valid git repository URL " full-url))))
 
 ;;=========================================
 ;; Internal: improving builtin autocomplete
@@ -768,9 +801,7 @@ USER-QUERY was the original query for this state update."
 
 
 (defun my-repo-pins--query-forge-fetchers (repo-query)
-  "Find repo matches to the relevant forges for REPO-QUERY then query forge.
-
-TODO: split that mess before 1.0. We shouldn't query here."
+  "Find repo matches to the relevant forges for REPO-QUERY then query forge."
   (let* ((parsed-repo-query (my-repo-pins--parse-repo-identifier repo-query))
          (repo-query-kind (alist-get 'tag parsed-repo-query)))
     (cond
@@ -790,19 +821,7 @@ TODO: split that mess before 1.0. We shouldn't query here."
                         (my-repo-pins--update-forges-state ,forge-str new-state ,repo-query)))))))
        my-repo-pins-forge-fetchers))
      ((equal repo-query-kind 'repo) (user-error "Can't checkout %s (for now), please specify a owner" repo-query))
-     ((equal repo-query-kind 'full-url)
-      (let*
-          ((code-root (my-repo-pins--safe-get-code-root))
-           (dest-dir (concat code-root (my-repo-pins--filepath-from-clone-url repo-query))))
-        (if (not (file-directory-p dest-dir))
-            (my-repo-pins--git-clone-in-dir
-             repo-query
-             dest-dir
-             (lambda (exit-code)
-               (if (equal exit-code 0)
-                   (find-file dest-dir)
-                 (error "Cannot clone %s" repo-query))))
-          (find-file dest-dir))))
+     ((equal repo-query-kind 'full-url) (my-repo-pins--clone-from-full-url repo-query))
      (t (error repo-query-kind)))))
 
 ;;=====================

tests/fixtures/dummy-git-repo/.git-to-rename/COMMIT_EDITMSG

@@ -0,0 +1,11 @@
+hello world
+# Veuillez saisir le message de validation pour vos modifications. Les lignes
+# commençant par '#' seront ignorées, et un message vide abandonne la validation.
+#
+# Sur la branche master
+#
+# Validation initiale
+#
+# Modifications qui seront validées :
+#	nouveau fichier : hello
+#

tests/fixtures/dummy-git-repo/.git-to-rename/HEAD

@@ -0,0 +1 @@
+ref: refs/heads/master

tests/fixtures/dummy-git-repo/.git-to-rename/config

@@ -0,0 +1,5 @@
+[core]
+	repositoryformatversion = 0
+	filemode = true
+	bare = false
+	logallrefupdates = true

tests/fixtures/dummy-git-repo/.git-to-rename/description

@@ -0,0 +1 @@
+Unnamed repository; edit this file 'description' to name the repository.

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/applypatch-msg.sample

@@ -0,0 +1,15 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to check the commit log message taken by
+# applypatch from an e-mail message.
+#
+# The hook should exit with non-zero status after issuing an
+# appropriate message if it wants to stop the commit.  The hook is
+# allowed to edit the commit message file.
+#
+# To enable this hook, rename this file to "applypatch-msg".
+
+. git-sh-setup
+commitmsg="$(git rev-parse --git-path hooks/commit-msg)"
+test -x "$commitmsg" && exec "$commitmsg" ${1+"$@"}
+:

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/commit-msg.sample

@@ -0,0 +1,24 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to check the commit log message.
+# Called by "git commit" with one argument, the name of the file
+# that has the commit message.  The hook should exit with non-zero
+# status after issuing an appropriate message if it wants to stop the
+# commit.  The hook is allowed to edit the commit message file.
+#
+# To enable this hook, rename this file to "commit-msg".
+
+# Uncomment the below to add a Signed-off-by line to the message.
+# Doing this in a hook is a bad idea in general, but the prepare-commit-msg
+# hook is more suited to it.
+#
+# SOB=$(git var GIT_AUTHOR_IDENT | sed -n 's/^\(.*>\).*$/Signed-off-by: \1/p')
+# grep -qs "^$SOB" "$1" || echo "$SOB" >> "$1"
+
+# This example catches duplicate Signed-off-by lines.
+
+test "" = "$(grep '^Signed-off-by: ' "$1" |
+	 sort | uniq -c | sed -e '/^[ 	]*1[ 	]/d')" || {
+	echo >&2 Duplicate Signed-off-by lines.
+	exit 1
+}

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/fsmonitor-watchman.sample

@@ -0,0 +1,174 @@
+#!/nix/store/facvd532b7igcfp3jdr6wjd56iaz9hr2-perl-5.36.0/bin/perl
+
+use strict;
+use warnings;
+use IPC::Open2;
+
+# An example hook script to integrate Watchman
+# (https://facebook.github.io/watchman/) with git to speed up detecting
+# new and modified files.
+#
+# The hook is passed a version (currently 2) and last update token
+# formatted as a string and outputs to stdout a new update token and
+# all files that have been modified since the update token. Paths must
+# be relative to the root of the working tree and separated by a single NUL.
+#
+# To enable this hook, rename this file to "query-watchman" and set
+# 'git config core.fsmonitor .git/hooks/query-watchman'
+#
+my ($version, $last_update_token) = @ARGV;
+
+# Uncomment for debugging
+# print STDERR "$0 $version $last_update_token\n";
+
+# Check the hook interface version
+if ($version ne 2) {
+	die "Unsupported query-fsmonitor hook version '$version'.\n" .
+	    "Falling back to scanning...\n";
+}
+
+my $git_work_tree = get_working_dir();
+
+my $retry = 1;
+
+my $json_pkg;
+eval {
+	require JSON::XS;
+	$json_pkg = "JSON::XS";
+	1;
+} or do {
+	require JSON::PP;
+	$json_pkg = "JSON::PP";
+};
+
+launch_watchman();
+
+sub launch_watchman {
+	my $o = watchman_query();
+	if (is_work_tree_watched($o)) {
+		output_result($o->{clock}, @{$o->{files}});
+	}
+}
+
+sub output_result {
+	my ($clockid, @files) = @_;
+
+	# Uncomment for debugging watchman output
+	# open (my $fh, ">", ".git/watchman-output.out");
+	# binmode $fh, ":utf8";
+	# print $fh "$clockid\n@files\n";
+	# close $fh;
+
+	binmode STDOUT, ":utf8";
+	print $clockid;
+	print "\0";
+	local $, = "\0";
+	print @files;
+}
+
+sub watchman_clock {
+	my $response = qx/watchman clock "$git_work_tree"/;
+	die "Failed to get clock id on '$git_work_tree'.\n" .
+		"Falling back to scanning...\n" if $? != 0;
+
+	return $json_pkg->new->utf8->decode($response);
+}
+
+sub watchman_query {
+	my $pid = open2(\*CHLD_OUT, \*CHLD_IN, 'watchman -j --no-pretty')
+	or die "open2() failed: $!\n" .
+	"Falling back to scanning...\n";
+
+	# In the query expression below we're asking for names of files that
+	# changed since $last_update_token but not from the .git folder.
+	#
+	# To accomplish this, we're using the "since" generator to use the
+	# recency index to select candidate nodes and "fields" to limit the
+	# output to file names only. Then we're using the "expression" term to
+	# further constrain the results.
+	my $last_update_line = "";
+	if (substr($last_update_token, 0, 1) eq "c") {
+		$last_update_token = "\"$last_update_token\"";
+		$last_update_line = qq[\n"since": $last_update_token,];
+	}
+	my $query = <<"	END";
+		["query", "$git_work_tree", {$last_update_line
+			"fields": ["name"],
+			"expression": ["not", ["dirname", ".git"]]
+		}]
+	END
+
+	# Uncomment for debugging the watchman query
+	# open (my $fh, ">", ".git/watchman-query.json");
+	# print $fh $query;
+	# close $fh;
+
+	print CHLD_IN $query;
+	close CHLD_IN;
+	my $response = do {local $/; <CHLD_OUT>};
+
+	# Uncomment for debugging the watch response
+	# open ($fh, ">", ".git/watchman-response.json");
+	# print $fh $response;
+	# close $fh;
+
+	die "Watchman: command returned no output.\n" .
+	"Falling back to scanning...\n" if $response eq "";
+	die "Watchman: command returned invalid output: $response\n" .
+	"Falling back to scanning...\n" unless $response =~ /^\{/;
+
+	return $json_pkg->new->utf8->decode($response);
+}
+
+sub is_work_tree_watched {
+	my ($output) = @_;
+	my $error = $output->{error};
+	if ($retry > 0 and $error and $error =~ m/unable to resolve root .* directory (.*) is not watched/) {
+		$retry--;
+		my $response = qx/watchman watch "$git_work_tree"/;
+		die "Failed to make watchman watch '$git_work_tree'.\n" .
+		    "Falling back to scanning...\n" if $? != 0;
+		$output = $json_pkg->new->utf8->decode($response);
+		$error = $output->{error};
+		die "Watchman: $error.\n" .
+		"Falling back to scanning...\n" if $error;
+
+		# Uncomment for debugging watchman output
+		# open (my $fh, ">", ".git/watchman-output.out");
+		# close $fh;
+
+		# Watchman will always return all files on the first query so
+		# return the fast "everything is dirty" flag to git and do the
+		# Watchman query just to get it over with now so we won't pay
+		# the cost in git to look up each individual file.
+		my $o = watchman_clock();
+		$error = $output->{error};
+
+		die "Watchman: $error.\n" .
+		"Falling back to scanning...\n" if $error;
+
+		output_result($o->{clock}, ("/"));
+		$last_update_token = $o->{clock};
+
+		eval { launch_watchman() };
+		return 0;
+	}
+
+	die "Watchman: $error.\n" .
+	"Falling back to scanning...\n" if $error;
+
+	return 1;
+}
+
+sub get_working_dir {
+	my $working_dir;
+	if ($^O =~ 'msys' || $^O =~ 'cygwin') {
+		$working_dir = Win32::GetCwd();
+		$working_dir =~ tr/\\/\//;
+	} else {
+		require Cwd;
+		$working_dir = Cwd::cwd();
+	}
+
+	return $working_dir;
+}

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/post-update.sample

@@ -0,0 +1,8 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to prepare a packed repository for use over
+# dumb transports.
+#
+# To enable this hook, rename this file to "post-update".
+
+exec git update-server-info

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/pre-applypatch.sample

@@ -0,0 +1,14 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to verify what is about to be committed
+# by applypatch from an e-mail message.
+#
+# The hook should exit with non-zero status after issuing an
+# appropriate message if it wants to stop the commit.
+#
+# To enable this hook, rename this file to "pre-applypatch".
+
+. git-sh-setup
+precommit="$(git rev-parse --git-path hooks/pre-commit)"
+test -x "$precommit" && exec "$precommit" ${1+"$@"}
+:

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/pre-commit.sample

@@ -0,0 +1,49 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to verify what is about to be committed.
+# Called by "git commit" with no arguments.  The hook should
+# exit with non-zero status after issuing an appropriate message if
+# it wants to stop the commit.
+#
+# To enable this hook, rename this file to "pre-commit".
+
+if git rev-parse --verify HEAD >/dev/null 2>&1
+then
+	against=HEAD
+else
+	# Initial commit: diff against an empty tree object
+	against=$(git hash-object -t tree /dev/null)
+fi
+
+# If you want to allow non-ASCII filenames set this variable to true.
+allownonascii=$(git config --type=bool hooks.allownonascii)
+
+# Redirect output to stderr.
+exec 1>&2
+
+# Cross platform projects tend to avoid non-ASCII filenames; prevent
+# them from being added to the repository. We exploit the fact that the
+# printable range starts at the space character and ends with tilde.
+if [ "$allownonascii" != "true" ] &&
+	# Note that the use of brackets around a tr range is ok here, (it's
+	# even required, for portability to Solaris 10's /usr/bin/tr), since
+	# the square bracket bytes happen to fall in the designated range.
+	test $(git diff --cached --name-only --diff-filter=A -z $against |
+	  LC_ALL=C tr -d '[ -~]\0' | wc -c) != 0
+then
+	cat <<\EOF
+Error: Attempt to add a non-ASCII file name.
+
+This can cause problems if you want to work with people on other platforms.
+
+To be portable it is advisable to rename the file.
+
+If you know what you are doing you can disable this check using:
+
+  git config hooks.allownonascii true
+EOF
+	exit 1
+fi
+
+# If there are whitespace errors, print the offending file names and fail.
+exec git diff-index --check --cached $against --

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/pre-merge-commit.sample

@@ -0,0 +1,13 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to verify what is about to be committed.
+# Called by "git merge" with no arguments.  The hook should
+# exit with non-zero status after issuing an appropriate message to
+# stderr if it wants to stop the merge commit.
+#
+# To enable this hook, rename this file to "pre-merge-commit".
+
+. git-sh-setup
+test -x "$GIT_DIR/hooks/pre-commit" &&
+        exec "$GIT_DIR/hooks/pre-commit"
+:

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/pre-push.sample

@@ -0,0 +1,53 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+
+# An example hook script to verify what is about to be pushed.  Called by "git
+# push" after it has checked the remote status, but before anything has been
+# pushed.  If this script exits with a non-zero status nothing will be pushed.
+#
+# This hook is called with the following parameters:
+#
+# $1 -- Name of the remote to which the push is being done
+# $2 -- URL to which the push is being done
+#
+# If pushing without using a named remote those arguments will be equal.
+#
+# Information about the commits which are being pushed is supplied as lines to
+# the standard input in the form:
+#
+#   <local ref> <local oid> <remote ref> <remote oid>
+#
+# This sample shows how to prevent push of commits where the log message starts
+# with "WIP" (work in progress).
+
+remote="$1"
+url="$2"
+
+zero=$(git hash-object --stdin </dev/null | tr '[0-9a-f]' '0')
+
+while read local_ref local_oid remote_ref remote_oid
+do
+	if test "$local_oid" = "$zero"
+	then
+		# Handle delete
+		:
+	else
+		if test "$remote_oid" = "$zero"
+		then
+			# New branch, examine all commits
+			range="$local_oid"
+		else
+			# Update to existing branch, examine new commits
+			range="$remote_oid..$local_oid"
+		fi
+
+		# Check for WIP commit
+		commit=$(git rev-list -n 1 --grep '^WIP' "$range")
+		if test -n "$commit"
+		then
+			echo >&2 "Found WIP commit in $local_ref, not pushing"
+			exit 1
+		fi
+	fi
+done
+
+exit 0

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/pre-rebase.sample

@@ -0,0 +1,169 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# Copyright (c) 2006, 2008 Junio C Hamano
+#
+# The "pre-rebase" hook is run just before "git rebase" starts doing
+# its job, and can prevent the command from running by exiting with
+# non-zero status.
+#
+# The hook is called with the following parameters:
+#
+# $1 -- the upstream the series was forked from.
+# $2 -- the branch being rebased (or empty when rebasing the current branch).
+#
+# This sample shows how to prevent topic branches that are already
+# merged to 'next' branch from getting rebased, because allowing it
+# would result in rebasing already published history.
+
+publish=next
+basebranch="$1"
+if test "$#" = 2
+then
+	topic="refs/heads/$2"
+else
+	topic=`git symbolic-ref HEAD` ||
+	exit 0 ;# we do not interrupt rebasing detached HEAD
+fi
+
+case "$topic" in
+refs/heads/??/*)
+	;;
+*)
+	exit 0 ;# we do not interrupt others.
+	;;
+esac
+
+# Now we are dealing with a topic branch being rebased
+# on top of master.  Is it OK to rebase it?
+
+# Does the topic really exist?
+git show-ref -q "$topic" || {
+	echo >&2 "No such branch $topic"
+	exit 1
+}
+
+# Is topic fully merged to master?
+not_in_master=`git rev-list --pretty=oneline ^master "$topic"`
+if test -z "$not_in_master"
+then
+	echo >&2 "$topic is fully merged to master; better remove it."
+	exit 1 ;# we could allow it, but there is no point.
+fi
+
+# Is topic ever merged to next?  If so you should not be rebasing it.
+only_next_1=`git rev-list ^master "^$topic" ${publish} | sort`
+only_next_2=`git rev-list ^master           ${publish} | sort`
+if test "$only_next_1" = "$only_next_2"
+then
+	not_in_topic=`git rev-list "^$topic" master`
+	if test -z "$not_in_topic"
+	then
+		echo >&2 "$topic is already up to date with master"
+		exit 1 ;# we could allow it, but there is no point.
+	else
+		exit 0
+	fi
+else
+	not_in_next=`git rev-list --pretty=oneline ^${publish} "$topic"`
+	/nix/store/facvd532b7igcfp3jdr6wjd56iaz9hr2-perl-5.36.0/bin/perl -e '
+		my $topic = $ARGV[0];
+		my $msg = "* $topic has commits already merged to public branch:\n";
+		my (%not_in_next) = map {
+			/^([0-9a-f]+) /;
+			($1 => 1);
+		} split(/\n/, $ARGV[1]);
+		for my $elem (map {
+				/^([0-9a-f]+) (.*)$/;
+				[$1 => $2];
+			} split(/\n/, $ARGV[2])) {
+			if (!exists $not_in_next{$elem->[0]}) {
+				if ($msg) {
+					print STDERR $msg;
+					undef $msg;
+				}
+				print STDERR " $elem->[1]\n";
+			}
+		}
+	' "$topic" "$not_in_next" "$not_in_master"
+	exit 1
+fi
+
+<<\DOC_END
+
+This sample hook safeguards topic branches that have been
+published from being rewound.
+
+The workflow assumed here is:
+
+ * Once a topic branch forks from "master", "master" is never
+   merged into it again (either directly or indirectly).
+
+ * Once a topic branch is fully cooked and merged into "master",
+   it is deleted.  If you need to build on top of it to correct
+   earlier mistakes, a new topic branch is created by forking at
+   the tip of the "master".  This is not strictly necessary, but
+   it makes it easier to keep your history simple.
+
+ * Whenever you need to test or publish your changes to topic
+   branches, merge them into "next" branch.
+
+The script, being an example, hardcodes the publish branch name
+to be "next", but it is trivial to make it configurable via
+$GIT_DIR/config mechanism.
+
+With this workflow, you would want to know:
+
+(1) ... if a topic branch has ever been merged to "next".  Young
+    topic branches can have stupid mistakes you would rather
+    clean up before publishing, and things that have not been
+    merged into other branches can be easily rebased without
+    affecting other people.  But once it is published, you would
+    not want to rewind it.
+
+(2) ... if a topic branch has been fully merged to "master".
+    Then you can delete it.  More importantly, you should not
+    build on top of it -- other people may already want to
+    change things related to the topic as patches against your
+    "master", so if you need further changes, it is better to
+    fork the topic (perhaps with the same name) afresh from the
+    tip of "master".
+
+Let's look at this example:
+
+		   o---o---o---o---o---o---o---o---o---o "next"
+		  /       /           /           /
+		 /   a---a---b A     /           /
+		/   /               /           /
+	       /   /   c---c---c---c B         /
+	      /   /   /             \         /
+	     /   /   /   b---b C     \       /
+	    /   /   /   /             \     /
+    ---o---o---o---o---o---o---o---o---o---o---o "master"
+
+
+A, B and C are topic branches.
+
+ * A has one fix since it was merged up to "next".
+
+ * B has finished.  It has been fully merged up to "master" and "next",
+   and is ready to be deleted.
+
+ * C has not merged to "next" at all.
+
+We would want to allow C to be rebased, refuse A, and encourage
+B to be deleted.
+
+To compute (1):
+
+	git rev-list ^master ^topic next
+	git rev-list ^master        next
+
+	if these match, topic has not merged in next at all.
+
+To compute (2):
+
+	git rev-list master..topic
+
+	if this is empty, it is fully merged to "master".
+
+DOC_END

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/pre-receive.sample

@@ -0,0 +1,24 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to make use of push options.
+# The example simply echoes all push options that start with 'echoback='
+# and rejects all pushes when the "reject" push option is used.
+#
+# To enable this hook, rename this file to "pre-receive".
+
+if test -n "$GIT_PUSH_OPTION_COUNT"
+then
+	i=0
+	while test "$i" -lt "$GIT_PUSH_OPTION_COUNT"
+	do
+		eval "value=\$GIT_PUSH_OPTION_$i"
+		case "$value" in
+		echoback=*)
+			echo "echo from the pre-receive-hook: ${value#*=}" >&2
+			;;
+		reject)
+			exit 1
+		esac
+		i=$((i + 1))
+	done
+fi

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/prepare-commit-msg.sample

@@ -0,0 +1,42 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to prepare the commit log message.
+# Called by "git commit" with the name of the file that has the
+# commit message, followed by the description of the commit
+# message's source.  The hook's purpose is to edit the commit
+# message file.  If the hook fails with a non-zero status,
+# the commit is aborted.
+#
+# To enable this hook, rename this file to "prepare-commit-msg".
+
+# This hook includes three examples. The first one removes the
+# "# Please enter the commit message..." help message.
+#
+# The second includes the output of "git diff --name-status -r"
+# into the message, just before the "git status" output.  It is
+# commented because it doesn't cope with --amend or with squashed
+# commits.
+#
+# The third example adds a Signed-off-by line to the message, that can
+# still be edited.  This is rarely a good idea.
+
+COMMIT_MSG_FILE=$1
+COMMIT_SOURCE=$2
+SHA1=$3
+
+/nix/store/facvd532b7igcfp3jdr6wjd56iaz9hr2-perl-5.36.0/bin/perl -i.bak -ne 'print unless(m/^. Please enter the commit message/..m/^#$/)' "$COMMIT_MSG_FILE"
+
+# case "$COMMIT_SOURCE,$SHA1" in
+#  ,|template,)
+#    /nix/store/facvd532b7igcfp3jdr6wjd56iaz9hr2-perl-5.36.0/bin/perl -i.bak -pe '
+#       print "\n" . `git diff --cached --name-status -r`
+# 	 if /^#/ && $first++ == 0' "$COMMIT_MSG_FILE" ;;
+#  *) ;;
+# esac
+
+# SOB=$(git var GIT_COMMITTER_IDENT | sed -n 's/^\(.*>\).*$/Signed-off-by: \1/p')
+# git interpret-trailers --in-place --trailer "$SOB" "$COMMIT_MSG_FILE"
+# if test -z "$COMMIT_SOURCE"
+# then
+#   /nix/store/facvd532b7igcfp3jdr6wjd56iaz9hr2-perl-5.36.0/bin/perl -i.bak -pe 'print "\n" if !$first_line++' "$COMMIT_MSG_FILE"
+# fi

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/push-to-checkout.sample

@@ -0,0 +1,78 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+
+# An example hook script to update a checked-out tree on a git push.
+#
+# This hook is invoked by git-receive-pack(1) when it reacts to git
+# push and updates reference(s) in its repository, and when the push
+# tries to update the branch that is currently checked out and the
+# receive.denyCurrentBranch configuration variable is set to
+# updateInstead.
+#
+# By default, such a push is refused if the working tree and the index
+# of the remote repository has any difference from the currently
+# checked out commit; when both the working tree and the index match
+# the current commit, they are updated to match the newly pushed tip
+# of the branch. This hook is to be used to override the default
+# behaviour; however the code below reimplements the default behaviour
+# as a starting point for convenient modification.
+#
+# The hook receives the commit with which the tip of the current
+# branch is going to be updated:
+commit=$1
+
+# It can exit with a non-zero status to refuse the push (when it does
+# so, it must not modify the index or the working tree).
+die () {
+	echo >&2 "$*"
+	exit 1
+}
+
+# Or it can make any necessary changes to the working tree and to the
+# index to bring them to the desired state when the tip of the current
+# branch is updated to the new commit, and exit with a zero status.
+#
+# For example, the hook can simply run git read-tree -u -m HEAD "$1"
+# in order to emulate git fetch that is run in the reverse direction
+# with git push, as the two-tree form of git read-tree -u -m is
+# essentially the same as git switch or git checkout that switches
+# branches while keeping the local changes in the working tree that do
+# not interfere with the difference between the branches.
+
+# The below is a more-or-less exact translation to shell of the C code
+# for the default behaviour for git's push-to-checkout hook defined in
+# the push_to_deploy() function in builtin/receive-pack.c.
+#
+# Note that the hook will be executed from the repository directory,
+# not from the working tree, so if you want to perform operations on
+# the working tree, you will have to adapt your code accordingly, e.g.
+# by adding "cd .." or using relative paths.
+
+if ! git update-index -q --ignore-submodules --refresh
+then
+	die "Up-to-date check failed"
+fi
+
+if ! git diff-files --quiet --ignore-submodules --
+then
+	die "Working directory has unstaged changes"
+fi
+
+# This is a rough translation of:
+#
+#   head_has_history() ? "HEAD" : EMPTY_TREE_SHA1_HEX
+if git cat-file -e HEAD 2>/dev/null
+then
+	head=HEAD
+else
+	head=$(git hash-object -t tree --stdin </dev/null)
+fi
+
+if ! git diff-index --quiet --cached --ignore-submodules $head --
+then
+	die "Working directory has staged changes"
+fi
+
+if ! git read-tree -u -m "$commit"
+then
+	die "Could not update working tree to new HEAD"
+fi

tests/fixtures/dummy-git-repo/.git-to-rename/hooks/update.sample

@@ -0,0 +1,128 @@
+#!/nix/store/y0g1mvsr6vygr61f9znljik9kl0x0inc-bash-5.1-p16/bin/bash
+#
+# An example hook script to block unannotated tags from entering.
+# Called by "git receive-pack" with arguments: refname sha1-old sha1-new
+#
+# To enable this hook, rename this file to "update".
+#
+# Config
+# ------
+# hooks.allowunannotated
+#   This boolean sets whether unannotated tags will be allowed into the
+#   repository.  By default they won't be.
+# hooks.allowdeletetag
+#   This boolean sets whether deleting tags will be allowed in the
+#   repository.  By default they won't be.
+# hooks.allowmodifytag
+#   This boolean sets whether a tag may be modified after creation. By default
+#   it won't be.
+# hooks.allowdeletebranch
+#   This boolean sets whether deleting branches will be allowed in the
+#   repository.  By default they won't be.
+# hooks.denycreatebranch
+#   This boolean sets whether remotely creating branches will be denied
+#   in the repository.  By default this is allowed.
+#
+
+# --- Command line
+refname="$1"
+oldrev="$2"
+newrev="$3"
+
+# --- Safety check
+if [ -z "$GIT_DIR" ]; then
+	echo "Don't run this script from the command line." >&2
+	echo " (if you want, you could supply GIT_DIR then run" >&2
+	echo "  $0 <ref> <oldrev> <newrev>)" >&2
+	exit 1
+fi
+
+if [ -z "$refname" -o -z "$oldrev" -o -z "$newrev" ]; then
+	echo "usage: $0 <ref> <oldrev> <newrev>" >&2
+	exit 1
+fi
+
+# --- Config
+allowunannotated=$(git config --type=bool hooks.allowunannotated)
+allowdeletebranch=$(git config --type=bool hooks.allowdeletebranch)
+denycreatebranch=$(git config --type=bool hooks.denycreatebranch)
+allowdeletetag=$(git config --type=bool hooks.allowdeletetag)
+allowmodifytag=$(git config --type=bool hooks.allowmodifytag)
+
+# check for no description
+projectdesc=$(sed -e '1q' "$GIT_DIR/description")
+case "$projectdesc" in
+"Unnamed repository"* | "")
+	echo "*** Project description file hasn't been set" >&2
+	exit 1
+	;;
+esac
+
+# --- Check types
+# if $newrev is 0000...0000, it's a commit to delete a ref.
+zero=$(git hash-object --stdin </dev/null | tr '[0-9a-f]' '0')
+if [ "$newrev" = "$zero" ]; then
+	newrev_type=delete
+else
+	newrev_type=$(git cat-file -t $newrev)
+fi
+
+case "$refname","$newrev_type" in
+	refs/tags/*,commit)
+		# un-annotated tag
+		short_refname=${refname##refs/tags/}
+		if [ "$allowunannotated" != "true" ]; then
+			echo "*** The un-annotated tag, $short_refname, is not allowed in this repository" >&2
+			echo "*** Use 'git tag [ -a | -s ]' for tags you want to propagate." >&2
+			exit 1
+		fi
+		;;
+	refs/tags/*,delete)
+		# delete tag
+		if [ "$allowdeletetag" != "true" ]; then
+			echo "*** Deleting a tag is not allowed in this repository" >&2
+			exit 1
+		fi
+		;;
+	refs/tags/*,tag)
+		# annotated tag
+		if [ "$allowmodifytag" != "true" ] && git rev-parse $refname > /dev/null 2>&1
+		then
+			echo "*** Tag '$refname' already exists." >&2
+			echo "*** Modifying a tag is not allowed in this repository." >&2
+			exit 1
+		fi
+		;;
+	refs/heads/*,commit)
+		# branch
+		if [ "$oldrev" = "$zero" -a "$denycreatebranch" = "true" ]; then
+			echo "*** Creating a branch is not allowed in this repository" >&2
+			exit 1
+		fi
+		;;
+	refs/heads/*,delete)
+		# delete branch
+		if [ "$allowdeletebranch" != "true" ]; then
+			echo "*** Deleting a branch is not allowed in this repository" >&2
+			exit 1
+		fi
+		;;
+	refs/remotes/*,commit)
+		# tracking branch
+		;;
+	refs/remotes/*,delete)
+		# delete tracking branch
+		if [ "$allowdeletebranch" != "true" ]; then
+			echo "*** Deleting a tracking branch is not allowed in this repository" >&2
+			exit 1
+		fi
+		;;
+	*)
+		# Anything else (is there anything else?)
+		echo "*** Update hook: unknown type of update to ref $refname of type $newrev_type" >&2
+		exit 1
+		;;
+esac
+
+# --- Finished
+exit 0

tests/fixtures/dummy-git-repo/.git-to-rename/info/exclude

@@ -0,0 +1,6 @@
+# git ls-files --others --exclude-from=.git/info/exclude
+# Lines that start with '#' are comments.
+# For a project mostly in C, the following would be a good set of
+# exclude patterns (uncomment them if you want to use them):
+# *.[oa]
+# *~

tests/fixtures/dummy-git-repo/.git-to-rename/logs/HEAD

@@ -0,0 +1 @@
+0000000000000000000000000000000000000000 1faa808d219f7d70e94deb7e864e5f57bf697e1d Félix Baylac-Jacqué <felix@alternativebit.fr> 1667988194 +0100	commit (initial): hello world

tests/fixtures/dummy-git-repo/.git-to-rename/logs/refs/heads/master

@@ -0,0 +1 @@
+0000000000000000000000000000000000000000 1faa808d219f7d70e94deb7e864e5f57bf697e1d Félix Baylac-Jacqué <felix@alternativebit.fr> 1667988194 +0100	commit (initial): hello world

tests/fixtures/dummy-git-repo/.git-to-rename/refs/heads/master

@@ -0,0 +1 @@
+1faa808d219f7d70e94deb7e864e5f57bf697e1d

tests/fixtures/dummy-git-repo/hello

@@ -0,0 +1 @@
+world