Change git repository structure.

Introduce one repository per configuration, so that many fewer git-add
and git-remove are necessary, speeding up things considerably.

Move the main git repository into a subdirectory of the main Cactus
directory.

Lock the git repository before calling git, so that parallel make
works.


git-svn-id: http://svn.cactuscode.org/arrangements/CactusUtils/Formaline/trunk@171 83718e91-0e4f-0410-abf4-91180603181f

4 files changed, 183 insertions, 256 deletions

diff --git a/src/make.code.deps b/src/make.code.deps
index 7f48ec8..7eb710f 100644
--- a/src/make.code.deps
+++ b/src/make.code.deps
@@ -8,7 +8,7 @@
 
 TARBALL_DIR = $(SCRATCH_BUILD)
 
-$(CCTK_TARGET): $(TARBALL_DIR)/gethostname.pl $(TARBALL_DIR)/makeblob.pl $(TARBALL_DIR)/makemetablob.pl $(TARBALL_DIR)/git-commit.pl
+$(CCTK_TARGET): $(TARBALL_DIR)/gethostname.pl $(TARBALL_DIR)/makeblob.pl $(TARBALL_DIR)/makemetablob.pl $(SCRATCH_BUILD)/git-lock.pl
 
 
 
@@ -21,5 +21,5 @@ $(TARBALL_DIR)/makeblob.pl: $(SRCDIR)/util/makeblob.pl
 $(TARBALL_DIR)/makemetablob.pl: $(SRCDIR)/util/makemetablob.pl
 	cd $(TARBALL_DIR) && cp $^ $@
 
-$(TARBALL_DIR)/git-commit.pl: $(SRCDIR)/util/git-commit.pl
-	cd $(TARBALL_DIR) && cp $^ $@
+$(SCRATCH_BUILD)/git-lock.pl: $(SRCDIR)/util/git-lock.pl
+	cd $(SCRATCH_BUILD) && cp $^ $@
diff --git a/src/make.configuration.deps b/src/make.configuration.deps
index d55d6a8..f1f5c66 100644
--- a/src/make.configuration.deps
+++ b/src/make.configuration.deps
@@ -57,6 +57,7 @@ $(FRM-LIB): $(FRM-OBJS)
 # (force a new ID to be created every time)
 # (do this after the thorn's library has been built, so that the
 #  script gethostname.pl has been copied to the scratch directory)
+# (generates also $(TOP)/CONFIG-ID)
 .PRECIOUS: $(TOP)/BUILD-ID
 $(TOP)/BUILD-ID: $(CCTK_LIBDIR)/$(LIBNAME_PREFIX)$(CCTK_LIBNAME_PREFIX)Formaline$(LIBNAME_SUFFIX)
 	config=`echo "$(EXE:cactus_%=%)" | $(TR_C) -d '[:alnum:]+-._]'` && \
@@ -77,13 +78,11 @@ $(TARBALL_DIR)/build-id.o: $(TARBALL_DIR)/build-id.c
 	$(CC) $(CFLAGS) -c -o $@ $^
 
 .PRECIOUS: $(TARBALL_DIR)/build-id.c
-$(TARBALL_DIR)/build-id.c: $(TOP)/BUILD-ID $(TOP)/GIT-COMMIT-ID
+$(TARBALL_DIR)/build-id.c: $(TOP)/BUILD-ID
 	{ \
 	echo '/* This is an auto-generated file -- do not edit */' && \
 	build_id="$$(cat $(TOP)/BUILD-ID)" && \
 	echo 'char const * const build_id = "'$$build_id'";' && \
-	git_commit_id="$$(cat $(TOP)/GIT-COMMIT-ID || echo 'NO-GIT-ID')" && \
-	echo 'char const * const source_id = "git-'$$git_commit_id'";' && \
 	config_id="$$(cat $(TOP)/CONFIG-ID || echo 'NO-CONFIG-ID')" && \
 	echo 'char const * const config_id = "'$$config_id'";'; \
 	} > $@
@@ -249,101 +248,148 @@ endif
 
 
 
-# Does git exist, or should we do nothing instead?
-GIT-REPO = $(CCTK_HOME)
-GIT-DIR = $(CCTK_HOME)/.git
-HAVE-GIT := $(shell env PATH=$$PATH:$$HOME/git/bin git --version > /dev/null 2>&1 && echo 'true' || echo 'false')
-GIT := $(shell $(HAVE-GIT) && echo 'env PATH=$$PATH:$$HOME/git/bin git' || { echo 'WARNING: git command not found' >&2 && echo 'true'; })
-
+# Suppress all output from git commands
+#GIT-SILENT = > /dev/null 2>&1
 
+# Does git exist, or should we do nothing instead?
+GIT-CMD := $(shell env PATH=$$PATH:$$HOME/git/bin which git)
+HAVE-GIT := $(shell '$(GIT-CMD)' --version > /dev/null 2>&1 && echo 'true' || echo 'false')
+GIT := $(shell $(HAVE-GIT) && echo '$(SCRATCH_BUILD)/git-lock.pl $(GIT-CMD) $(GIT-SILENT)' || { echo 'WARNING: git command not found' >&2 && echo 'true'; })
 
-$(EXEDIR)$(DIRSEP)$(EXE): git-commit
 
-.PHONY: git-commit
-git-commit: $(TOP)/GIT-COMMIT-ID
 
 ifeq ($(HAVE-GIT),true)
 
-.PRECIOUS: $(TOP)/GIT-COMMIT-ID
-$(TOP)/GIT-COMMIT-ID: $(TOP)/BUILD-ID $(TARBALL_DIR)/cactus-flesh-source.files $(patsubst %,$(TARBALL_DIR)/cactus-thorn-source-%.files,$(notdir $(THORNS)))
-	$(TARBALL_DIR)/git-commit.pl --git='$(GIT)' --git-repo='$(GIT-REPO)' \
-		--CCTK_HOME='$(CCTK_HOME)' --TOP='$(TOP)' \
-		--TARBALL_DIR='$(TARBALL_DIR)' \
-		$(notdir $(THORNS))
-
-unused-$(TOP)/GIT-COMMIT-ID: $(TOP)/BUILD-ID $(TARBALL_DIR)/cactus-flesh-source.files $(patsubst %,$(TARBALL_DIR)/cactus-thorn-source-%.files,$(notdir $(THORNS)))
-	cd $(GIT-REPO) && \
-	true "Ensure that the git repository exists" && \
-	if ! test -e $(GIT-DIR) -a -e $(GIT-DIR)/HEAD; then \
-		mkdir -p $(GIT-DIR) && \
-		echo "Formaline: Creating new git repository..." && \
-		$(GIT) init && \
-		true "Add a root commit to please some tools" && \
-		: >> README && \
-		$(GIT) add README && \
-		$(GIT) commit -m 'README'; \
+main: git-store-source
+
+.PHONY: git-store-source
+git-store-source: git-commit-everything git-push-everything
+	echo "Formaline: Done."
+
+GIT-ROOT        = $(CCTK_HOME)
+GIT-REPO        = $(TOP)/configjar.git
+GIT-MASTER-REPO = $(CCTK_HOME)/cactusjar.git
+
+GIT-THORNS      = $(notdir $(THORNS))
+
+BUILD-ID-FILE   = $(TOP)/BUILD-ID
+CONFIG-ID-FILE  = $(TOP)/CONFIG-ID
+
+define GIT-INIT-MASTER-REPO
+	if [ ! -e $(GIT-MASTER-REPO)/.git/HEAD ]; then \
+		echo "Formaline: Creating master git repository..." && \
+		mkdir -p $(GIT-MASTER-REPO) && \
+		cd $(GIT-MASTER-REPO) && \
+		$(GIT) init-db; \
+	fi
+endef
+
+define GIT-INIT-REPO
+	if [ ! -e $(GIT-REPO)/.git/HEAD ]; then \
+		echo "Formaline: Creating git repository..." && \
+		mkdir -p $(GIT-REPO) && \
+		cd $(GIT-REPO) && \
+		$(GIT) init-db; \
+	fi
+endef
+
+.PHONY: git-push-everything
+git-push-everything: git-commit-everything $(BUILD-ID-FILE)
+	$(GIT-INIT-MASTER-REPO)
+	echo "Formaline: Pushing source tree to master git repository..." && \
+	cd $(GIT-ROOT) && \
+	export GIT_DIR=$(GIT-REPO)/.git && \
+	build_id=$$(cat $(BUILD-ID-FILE)) && \
+	$(GIT) push -f $(GIT-MASTER-REPO) "$$build_id" && \
+	config_id=$$(cat $(CONFIG-ID-FILE)) && \
+	$(GIT) push -f $(GIT-MASTER-REPO) "$$config_id"
+	cd $(GIT-ROOT) && \
+	export GIT_DIR=$(GIT-MASTER-REPO)/.git && \
+	echo "Formaline: Optimising master git repository..." && \
+	$(GIT) gc
+	if [ -e "$(CCTK_HOME)/cactus.config" ]; then \
+		source "$(CCTK_HOME)/cactus.config"; \
 	fi && \
-	true "Remove all staged files" && \
-	echo "Formaline: Preparing git repository..." && \
-	$(GIT) rm --cached -r . > /dev/null 2>&1; \
+	if [ -n "$$CACTUS_CENTRAL_GIT_REPO" ]; then \
+		cd $(GIT-ROOT) && \
+		export GIT_DIR=$(GIT-MASTER-REPO)/.git && \
+		echo "Formaline: Pushing to central repository $$CACTUS_CENTRAL_GIT_REPO..." && \
+		config_id=$$(cat $(CONFIG-ID-FILE)) && \
+		{ $(GIT) tag -l && echo "$$config_id"; } | \
+		xargs $(GIT) push -f "$$CACTUS_CENTRAL_GIT_REPO"; \
+	fi
+
+# Try to use the previous commit as parent, if possible
+.PHONY: git-commit-everything
+git-commit-everything: $(SCRATCH_BUILD)/cactus-flesh-source.git-tag $(GIT-THORNS:%=$(SCRATCH_BUILD)/cactus-thorn-%.git-tag) $(BUILD-ID-FILE)
+	echo "Formaline: Committing source tree to git repository..." && \
+	cd $(GIT-ROOT) && \
+	export GIT_DIR=$(GIT-REPO)/.git && \
+	build_id="$$(cat $(BUILD-ID-FILE))" && \
+	{ $(GIT) commit -m "$$build_id" || true; } && \
+	$(GIT) tag -f "$$build_id" && \
+	echo "Formaline: Created git tag $$build_id" && \
+	config_id="$$(cat $(CONFIG-ID-FILE))" && \
+	$(GIT) branch -f "$$config_id" && \
+	echo "Formaline: Updated git branch $$config_id" && \
+	echo "Formaline: Optimising git repository (slow only the first time)..." && \
+	$(GIT) gc
+
+.PRECIOUS: $(SCRATCH_BUILD)/cactus-flesh-source.git-tag
+$(SCRATCH_BUILD)/cactus-flesh-source.git-tag: $(TARBALL_DIR)/cactus-flesh-source.files
+	$(GIT-INIT-REPO)
 	echo "Formaline: Adding flesh to git repository..." && \
+	cd $(GIT-ROOT) && \
+	export GIT_DIR=$(GIT-REPO)/.git && \
+	{ $(GIT) rm --cached -r CONTRIBUTORS COPYRIGHT Makefile lib src configs > /dev/null 2>&1 || true; } && \
 	xargs ls < $(TARBALL_DIR)/cactus-flesh-source.files \
 		> $(TARBALL_DIR)/cactus-flesh-source.files2 2> /dev/null; \
 	xargs $(GIT) add < $(TARBALL_DIR)/cactus-flesh-source.files2 && \
 	rm $(TARBALL_DIR)/cactus-flesh-source.files2 && \
-	for thorn in $(notdir $(THORNS)); do \
-		echo "Formaline: Adding thorn $$thorn to git repository..." && \
-		xargs ls < $(TARBALL_DIR)/cactus-thorn-source-$$thorn.files \
-			> $(TARBALL_DIR)/cactus-thorn-source-$$thorn.files2 \
-			2> /dev/null; \
-		xargs $(GIT) add \
-			< $(TARBALL_DIR)/cactus-thorn-source-$$thorn.files2 && \
-		rm $(TARBALL_DIR)/cactus-thorn-source-$$thorn.files2; \
-	done && \
-	true "Write source tree and create a commit" && \
-	echo "Formaline: Committing source tree to git repository..." && \
-	$(GIT) add configs/$(notdir $(TOP))/BUILD-ID && \
-	$(GIT) write-tree > $(TARBALL_DIR)/GIT-TREE-ID && \
-	true "Try to use the previous commit as parent, if possible" && \
-	if test -e $@ -a -n "$$(cat $@)"; then \
-		$(GIT) commit-tree $$(cat $(TARBALL_DIR)/GIT-TREE-ID) -p "$$(cat $@)" < $(TOP)/BUILD-ID > $@.new || \
-		$(GIT) commit-tree $$(cat $(TARBALL_DIR)/GIT-TREE-ID)                 < $(TOP)/BUILD-ID > $@.new; \
-	else \
-		$(GIT) commit-tree $$(cat $(TARBALL_DIR)/GIT-TREE-ID)                 < $(TOP)/BUILD-ID > $@.new; \
-	fi && \
-	mv $@.new $@ && \
-	true "Remember the commit id" && \
-	mkdir -p $(CCTK_HOME)/GIT-COMMIT-IDS && \
-	cp $@ $(CCTK_HOME)/GIT-COMMIT-IDS/$$(cat $@) && \
-	echo "Formaline: Git commit id is $$(cat $@)" && \
-	true "Update branch" && \
-	config_id=$$(cat $(TOP)/CONFIG-ID) && \
-	$(GIT) branch -f $$config_id $$(cat $@) && \
-	echo "Formaline: Cleaning up git repository..." && \
-	$(GIT) rm --cached -r . > /dev/null 2>&1; \
-	true "Call git-gc for good measure" && \
-	echo "Formaline: Optimising git repository (slow only the first time)..." && \
-	$(GIT) gc > /dev/null 2>&1 && \
-	echo "Formaline: Done."; \
+	: > $@
+
+.PRECIOUS: $(SCRATCH_BUILD)/cactus-thorn-%.git-tag
+$(SCRATCH_BUILD)/cactus-thorn-%.git-tag: $(TARBALL_DIR)/cactus-thorn-source-%.files
+	$(GIT-INIT-REPO)
+	echo "Formaline: Adding thorn $* to git repository..." && \
+	cd $(GIT-ROOT) && \
+	export GIT_DIR=$(GIT-REPO)/.git && \
+	{ $(GIT) rm --cached -r arrangements/*/$* > /dev/null 2>&1 || true; } &&\
+	xargs ls < $(TARBALL_DIR)/cactus-thorn-source-$*.files \
+		> $(TARBALL_DIR)/cactus-thorn-source-$*.files2 2> /dev/null; \
+	xargs $(GIT) add < $(TARBALL_DIR)/cactus-thorn-source-$*.files2 && \
+	rm $(TARBALL_DIR)/cactus-thorn-source-$*.files2 && \
+	: > $@
 
-else
+endif
 
-.PRECIOUS: $(TOP)/GIT-COMMIT-ID
-$(TOP)/GIT-COMMIT-ID: $(TOP)/BUILD-ID $(TARBALL_DIR)/cactus-flesh-source.files $(patsubst %,$(TARBALL_DIR)/cactus-thorn-source-%.files,$(notdir $(THORNS)))
-	echo 'NO-GIT-ID' > $(TOP)/GIT-COMMIT-ID
 
-endif
+
+# NOTE:
+
+# Define environment variable CACTUS_CENTRAL_GIT_REPO where the source trees
+# are automatically pushed
+
+# git-archive --prefix=Cactus/ wavetoy | gzip > wavetoy.tar.gz
+# git-archive --prefix=Cactus/ wavetoy | { cd /somewhere && tar xf -; }
+
+# git init
+# git pull <repo> <branch>
+
+# git clone <repo>
+# git checkout <tag>
 
 
 
 # TODO:
-# 1. Remember git-archive to get a tarball
-# 2. Don't create a version history; instead, leave all commits independent
 # 3. Push the commits automatically to a central (write-only?) repository
+
+# DONE:
+# 1. Remember git-archive to get a tarball
 # 4. What if the Cactus directory is alread the root of a git repository?
 # 5. Place the .git repository into the config subdirectory
 # 6. Push it automatically into a subdirectory of the main Cactus directory
 # 7. Figure out how to handle conflicting branch names
 
-# git-archive --prefix=Cactus/ wavetoy | gzip > wavetoy.tar.gz
-# git-archive --prefix=Cactus/ wavetoy | { cd /somewhere && tar xf -; }
+# WONT:
+# 2. Don't create a version history; instead, leave all commits independent
diff --git a/src/util/git-commit.pl b/src/util/git-commit.pl
deleted file mode 100755
index d28e023..0000000
--- a/src/util/git-commit.pl
+++ /dev/null
@@ -1,177 +0,0 @@
-#! /usr/bin/perl -w
-
-# Commit the current source tree to a git repository
-
-# 2008-03-02 Erik Schnetter <schnetter@cct.lsu.edu>
-
-use strict;
-#use Fcntl ':flock';
-use Getopt::Long;
-
-# $(GIT-REPO)
-# $(CCTK-HOME)
-# $(CONFIG-DIR)
-# $(SCRATCH-DIR)
-
-my %options;
-GetOptions
-    (\%options,
-     'git=s',                   # git command
-     'git-repo=s',              # git repository
-     'CCTK_HOME=s',             # main Cactus directory
-     'TOP=s',                   # main directory of the configuration
-     'TARBALL_DIR=s',           # Formaline's directory
-    ) or die "Could not parse command line options";
-
-my $git         = $options{'git'};
-my $git_repo    = $options{'git-repo'};
-my $cctk_home   = $options{'CCTK_HOME'};
-my $config_dir  = $options{'TOP'};
-my $tarball_dir = $options{'TARBALL_DIR'};
-
-defined $git         or die;
-defined $git_repo    or die;
-defined $cctk_home   or die;
-defined $config_dir  or die;
-defined $tarball_dir or die;
-
-chdir $git_repo or die;
-
-# Use relative path names
-$config_dir =~ m+/configs/+;
-$config_dir = "configs/$'";
-
-my $config_id_file = "$config_dir/CONFIG-ID";
-my $build_id_file  = "$config_dir/BUILD-ID";
-my $commit_id_file = "$config_dir/GIT-COMMIT-ID";
-
-my @thorns = @ARGV;
-
-
-
-# Obtain exclusive access to the repository
-
-# We cannot use flock since the file system may be remote
-#open LOCKFILE, "$cctk_home/Makefile";
-#flock LOCKFILE, LOCK_EX;
-
-my $gitlock = "$cctk_home/GITLOCK";
-my $waittime = 1;
-my $maxwaittime = 30;
-while (! (mkdir $gitlock)) {
-    # Check whether the locking process still exists
-    my $pid = `cat $gitlock/PID`;
-    chomp $pid;
-    if ($pid ne '') {
-        system "ps $pid > /dev/null 2>&1";
-        if ($?) {
-            # Break the lock
-            print "Git repository seems free -- breaking the lock\n";
-            unlink "$gitlock/PID" or die;
-            rmdir "$gitlock" or die;
-            $waittime = 1;
-            next;
-        }
-    }
-    # Wait some time
-    my $unit = $waittime==1 ? "second" : "seconds";
-    print "Git repository is busy; waiting $waittime $unit...\n";
-    system "sleep $waittime";
-    # Back off exponentially
-    $waittime *= 2;
-    $waittime = $maxwaittime if $waittime > $maxwaittime;
-}
-# Ensure that the lock exists
-die unless -d $gitlock;
-# Add our PID
-open PID, '>', "$gitlock/PID.tmp" or die;
-print PID "$$\n";
-close PID;
-rename "$gitlock/PID.tmp", "$gitlock/PID" or die;
-# Check whether it is really our PID
-my $pid = `cat $gitlock/PID`;
-chomp $pid;
-die unless $pid == $$;
-
-
-
-# Ensure that the git repository exists
-if (! -e "$git_repo/.git/HEAD") {
-    print "Formaline: Creating new git repository...\n";
-    system "$git init"; $? and die;
-    # Add a root commit to please some tools
-    system ": >> README"; $? and die;
-    system "$git add README"; $? and die;
-    system "$git commit -m 'README'"; $? and die;
-}
-
-# Remove all staged files
-print "Formaline: Preparing git repository...\n";
-system "$git rm --cached -r . > /dev/null 2>&1"; # may fail
-
-# Add flesh files to repository
-print "Formaline: Adding flesh to git repository...\n";
-system "xargs ls < $tarball_dir/cactus-flesh-source.files > $tarball_dir/cactus-flesh-source.files.tmp 2> /dev/null"; $? and die;
-system "xargs $git add < $tarball_dir/cactus-flesh-source.files.tmp"; $? and die;
-unlink "$tarball_dir/cactus-flesh-source.files.tmp" or die;
-
-# Add thorn files to repository
-foreach my $thorn (@thorns) {
-    print "Formaline: Adding thorn $thorn to git repository...\n";
-    system "xargs ls < $tarball_dir/cactus-thorn-source-$thorn.files > $tarball_dir/cactus-thorn-source-$thorn.files.tmp 2> /dev/null"; $? and die;
-    system "xargs $git add < $tarball_dir/cactus-thorn-source-$thorn.files.tmp"; $? and die;
-    unlink "$tarball_dir/cactus-thorn-source-$thorn.files.tmp" or die;
-}
-
-# Write source tree and create a commit
-print "Formaline: Committing source tree to git repository...\n";
-system "$git add $config_id_file $build_id_file"; $? and die;
-my $tree_id_file = "$tarball_dir/GIT-TREE-ID";
-system "$git write-tree > $tree_id_file"; $? and die;
-my $tree_id = `cat $tree_id_file`;
-chomp $tree_id;
-
-# Try to use the previous commit as parent, if possible
-my $old_commit_id;
-if (-e $commit_id_file) {
-    $old_commit_id = `cat $commit_id_file`;
-    chomp $old_commit_id;
-}
-
-# (Use the build id as commit message)
-my $did_commit = 0;
-if (defined $old_commit_id && $old_commit_id ne '') {
-    system "$git commit-tree $tree_id -p $old_commit_id < $build_id_file > $commit_id_file.new";
-    $did_commit = $? == 0;
-}
-if (! $did_commit) {
-    system "$git commit-tree $tree_id < $build_id_file > $commit_id_file.new"; $? and die;
-}
-rename "$commit_id_file.new", "$commit_id_file" or die;
-my $commit_id = `cat $commit_id_file`;
-chomp $commit_id;
-print "Formaline: Git commit id is $commit_id\n";
-
-# Remember the commit id
-mkdir "$cctk_home/GIT-COMMIT-IDS";
-system "cp $commit_id_file $cctk_home/GIT-COMMIT-IDS/$commit_id"; $? and die;
-
-# Update branch
-my $config_id = `cat $config_id_file`;
-chomp $config_id;
-die unless defined $config_id && $config_id ne '';
-system "$git branch -f $config_id $commit_id"; $? and die;
-
-print "Formaline: Cleaning up git repository...\n";
-system "$git rm --cached -r . > /dev/null 2>&1"; # may fail
-
-# Call git-gc for good measure
-print "Formaline: Optimising git repository (slow only the first time)...\n";
-system "$git gc > /dev/null 2>&1"; $? and die;
-
-
-
-# Release the lock
-system "rm -rf $gitlock";
-
-print "Formaline: Done.\n";
diff --git a/src/util/git-lock.pl b/src/util/git-lock.pl
new file mode 100755
index 0000000..0eb7922
--- /dev/null
+++ b/src/util/git-lock.pl
@@ -0,0 +1,58 @@
+#! /usr/bin/perl -w
+
+# Obtain a lock for a git repository
+
+# 2008-03-06 Erik Schnetter <schnetter@cct.lsu.edu>
+
+use strict;
+use Cwd;
+#use Fcntl ':flock';
+use sigtrap qw(die normal-signals);
+
+
+
+# Obtain exclusive access to the repository
+
+# We cannot use flock since the file system may be remote
+#open LOCKFILE, "$cctk_home/Makefile";
+#flock LOCKFILE, LOCK_EX;
+
+my $git_dir = $ENV{'GIT_DIR'};
+$git_dir = getcwd unless defined $git_dir;
+$git_dir =~ s+/.git/*$+/+;
+
+# We are very conservative as to what characters we allow.  Other
+# characters can be added, but be careful.
+$git_dir =~ m|^[[:alnum:]+-._/]+$| or die;
+
+my $lockdir = "$git_dir/GITLOCK";
+
+
+
+my $waittime = 1;
+my $maxwaittime = 10;
+while (! (mkdir $lockdir)) {
+    # Wait some time
+    my $unit = $waittime==1 ? "second" : "seconds";
+    print "Git repository is busy; waiting $waittime $unit...\n";
+    system "sleep $waittime";
+    # Back off exponentially
+    $waittime *= 2;
+    $waittime = $maxwaittime if $waittime > $maxwaittime;
+}
+
+
+
+# Execute the command
+system @ARGV;
+$? != -1 or die;
+exit $? >> 8;
+
+
+
+# Release the lock
+END {
+    my $retval = $?;
+    rmdir $lockdir;
+    $? = $retval;
+}