+sub git_reflog_action_msg ($) {
+ my ($msg) = @_;
+ my $rla = $ENV{GIT_REFLOG_ACTION};
+ $msg = "$rla: $msg" if length $rla;
+ return $msg;
+}
+
+sub git_update_ref_cmd {
+ # returns qw(git update-ref), qw(-m), @_
+ # except that message may be modified to honour GIT_REFLOG_ACTION
+ my $msg = shift @_;
+ $msg = git_reflog_action_msg $msg;
+ return qw(git update-ref -m), $msg, @_;
+}
+
+sub changedir ($) {
+ my ($newdir) = @_;
+ printdebug "CD $newdir\n";
+ chdir $newdir or confess "chdir: $newdir: $!";
+}
+
+sub git_slurp_config_src ($) {
+ my ($src) = @_;
+ # returns $r such that $r->{KEY}[] = VALUE
+ my @cmd = (qw(git config -z --get-regexp), "--$src", qw(.*));
+ debugcmd "|",@cmd;
+
+ local ($debuglevel) = $debuglevel-2;
+ local $/="\0";
+
+ my $r = { };
+ open GITS, "-|", @cmd or die $!;
+ while (<GITS>) {
+ chomp or die;
+ printdebug "=> ", (messagequote $_), "\n";
+ m/\n/ or die "$_ ?";
+ push @{ $r->{$`} }, $'; #';
+ }
+ $!=0; $?=0;
+ close GITS
+ or ($!==0 && $?==256)
+ or failedcmd @cmd;
+ return $r;
+}
+
+sub gdr_ffq_prev_branchinfo ($) {
+ my ($symref) = @_;
+ # => ('status', "message", [$symref, $ffq_prev, $gdrlast])
+ # 'status' may be
+ # branch message is undef
+ # weird-symref } no $symref,
+ # notbranch } no $ffq_prev
+ return ('detached', 'detached HEAD') unless defined $symref;
+ return ('weird-symref', 'HEAD symref is not to refs/')
+ unless $symref =~ m{^refs/};
+ my $ffq_prev = "refs/$ffq_refprefix/$'";
+ my $gdrlast = "refs/$gdrlast_refprefix/$'";
+ printdebug "ffq_prev_branchinfo branch current $symref\n";
+ return ('branch', undef, $symref, $ffq_prev, $gdrlast);
+}
+
+# ========== playground handling ==========
+
+# terminology:
+#
+# $maindir user's git working tree
+# playground area in .git/ where we can make files, unpack, etc. etc.
+# playtree git working tree sharing object store with the user's
+# inside playground, or identical to it
+#
+# other globals
+#
+# $local_git_cfg hash of arrays of values: git config from $maindir
+#
+# expected calling pattern
+#
+# firstly
+#
+# [record_maindir]
+# must be run in directory containing .git
+# assigns to $maindir if not already set
+# also calls git_slurp_config_src to record git config
+# in $local_git_cfg, unless it's already set
+#
+# fresh_playground SUBDIR_PATH_COMPONENTS
+# e.g fresh_playground 'dgit/unpack' ('.git/' is implied)
+# default SUBDIR_PATH_COMPONENTS is playground_subdir
+# calls record_maindir
+# sets up a new playground (destroying any old one)
+# returns playground pathname
+# caller may call multiple times with different subdir paths
+# createing different playgrounds
+#
+# ensure_a_playground SUBDIR_PATH_COMPONENTS
+# like fresh_playground except:
+# merely ensures the directory exists; does not delete an existing one
+#
+# then can use
+#
+# changedir playground
+# changedir $maindir
+#
+# playtree_setup $local_git_cfg
+# # ^ call in some (perhaps trivial) subdir of playground
+#
+# rmtree playground
+
+# ----- maindir -----
+
+# these three all go together
+our $maindir;
+our $maindir_gitdir;
+our $maindir_gitcommon;
+
+our $local_git_cfg;
+
+sub record_maindir () {
+ if (!defined $maindir) {
+ $maindir = must_getcwd();
+ if (!stat "$maindir/.git") {
+ fail "cannot stat $maindir/.git: $!";
+ }
+ if (-d _) {
+ # we fall back to this in case we have a pre-worktree
+ # git, which may not know git rev-parse --git-common-dir
+ $maindir_gitdir = "$maindir/.git";
+ $maindir_gitcommon = "$maindir/.git";
+ } else {
+ $maindir_gitdir = cmdoutput qw(git rev-parse --git-dir);
+ $maindir_gitcommon = cmdoutput qw(git rev-parse --git-common-dir);
+ }
+ }
+ $local_git_cfg //= git_slurp_config_src 'local';
+}
+
+# ----- playgrounds -----
+
+sub ensure_a_playground_parent ($) {
+ my ($spc) = @_;
+ record_maindir();
+ $spc = "$maindir_gitdir/$spc";
+ my $parent = dirname $spc;
+ mkdir $parent or $!==EEXIST
+ or fail "failed to mkdir playground parent $parent: $!";
+ return $spc;
+}
+
+sub ensure_a_playground ($) {
+ my ($spc) = @_;
+ $spc = ensure_a_playground_parent $spc;
+ mkdir $spc or $!==EEXIST or fail "failed to mkdir a playground $spc: $!";
+ return $spc;
+}
+
+sub fresh_playground ($) {
+ my ($spc) = @_;
+ $spc = ensure_a_playground_parent $spc;
+ rmtree $spc;
+ mkdir $spc or fail "failed to mkdir the playground $spc: $!";
+ return $spc;
+}
+
+# ----- playtrees -----
+
+sub playtree_setup (;$) {
+ my ($t_local_git_cfg) = @_;
+ $t_local_git_cfg //= $local_git_cfg;
+ # for use in the playtree
+ # $maindir must be set, eg by calling record_maindir or fresh_playground
+ runcmd qw(git init -q);
+ runcmd qw(git config gc.auto 0);
+ foreach my $copy (qw(user.email user.name user.useConfigOnly
+ core.sharedRepository
+ core.compression core.looseCompression
+ core.bigFileThreshold core.fsyncObjectFiles)) {
+ my $v = $t_local_git_cfg->{$copy};
+ next unless $v;
+ runcmd qw(git config), $copy, $_ foreach @$v;
+ }
+ # this is confusing: we have
+ # . playtree, not a worktree, has .git/, our cwd
+ # $maindir might be a worktree so
+ # $maindir_gitdir contains our main working "dgit", HEAD, etc.
+ # $maindir_gitcommon the shared stuff, including .objects
+ rmtree('.git/objects');
+ symlink "$maindir_gitcommon/objects",'.git/objects' or die $!;
+ ensuredir '.git/info';
+ open GA, "> .git/info/attributes" or die $!;
+ print GA "* $negate_harmful_gitattrs\n" or die $!;
+ close GA or die $!;
+}
+