playground refactoring: Dgit.pm: Provide ensure_a_playground

[dgit.git] / Debian / Dgit.pm

diff --git a/Debian/Dgit.pm b/Debian/Dgit.pm
index 515a32f600b805634a8b3991e21b702c603dc56d..de37261d1820b86d54e874860932be631ab2f135 100644 (file)
--- a/Debian/Dgit.pm
+++ b/Debian/Dgit.pm
@@ -30,6 +30,7 @@ use Digest::SHA;
 use Data::Dumper;
 use IPC::Open2;
 use File::Path;
+use File::Basename;
 
 BEGIN {
     use Exporter   ();
@@ -62,7 +63,9 @@ BEGIN {
                      playtree_setup);
     # implicitly uses $main::us
     %EXPORT_TAGS = ( policyflags => [qw(NOFFCHECK FRESHREPO NOCOMMITCHECK)],
-                    playground => [qw($local_git_cfg)]);
+                    playground => [qw(record_maindir $maindir $local_git_cfg
+                                      fresh_playground $playground
+                                       ensure_a_playground)]);
     @EXPORT_OK   = ( @{ $EXPORT_TAGS{policyflags} },
                     @{ $EXPORT_TAGS{playground} } );
 }
@@ -458,16 +461,97 @@ sub git_slurp_config_src ($) {
 
 # ========== 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)
+#      assigns to $playground and returns the same pathname
+#      caller may call multiple times with different subdir paths
+#       createing different playgrounds; but $playground global can
+#       refer only to one, obv.
+#
+#    ensure_a_playground SUBDIR_PATH_COMPONENTS
+#      like fresh_playground except:
+#      merely ensures the directory exists; does not delete an existing one
+#      never sets global $playground
+#
+#  then can use
+#
+#    changedir $playground
+#    changedir $maindir
+#
+#    playtree_setup $local_git_cfg
+#            # ^ call in some (perhaps trivial) subdir of $playground
+#
+#    rmtree $playground
+
+# ----- maindir -----
 
+our $maindir;
 our $local_git_cfg;
 
+sub record_maindir () {
+    $maindir //= must_getcwd();
+    $local_git_cfg //= git_slurp_config_src 'local';
+}
+
+# ----- playgrounds -----
+
+our $playground;
+
+sub ensure_a_playground_parent ($) {
+    my ($spc) = @_;
+    record_maindir();
+    $spc = ".git/$spc";
+    my $parent = dirname $spc;
+    mkdir $parent or $!==EEXIST or fail "failed to mkdir $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 $spc or die "$spc $!";
+    return $playground = "$maindir/$spc";
+}
+
 # ----- playtrees -----
 
 sub playtree_setup (;$) {
     my ($t_local_git_cfg) = @_;
     $t_local_git_cfg //= $local_git_cfg;
-    # should be run in a directory .git/FOO/BAR of a working tree
+    # 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 $copy (qw(user.email user.name user.useConfigOnly
@@ -479,7 +563,7 @@ sub playtree_setup (;$) {
        runcmd qw(git config), $copy, $_ foreach @$v;
     }
     rmtree('.git/objects');
-    symlink '../../../../objects','.git/objects' or die $!;
+    symlink "$maindir/.git/objects",'.git/objects' or die $!;
     ensuredir '.git/info';
     open GA, "> .git/info/attributes" or die $!;
     print GA "* $negate_harmful_gitattrs\n" or die $!;