import first prototype

diff --git a/tg-datastore b/tg-datastore
new file mode 100755 (executable)
index 0000000..e9ce139
--- /dev/null
+++ b/tg-datastore
@@ -0,0 +1,47 @@
+#!/bin/sh
+set -eu
+
+. ${0%/*}/tg-datastore.inc
+
+info() { printf "I: $@\n" >&2; }
+
+case "$1" in
+  add)
+    # tg-datastore add var=val var2=val2 ...
+    # only add to HEAD
+    shift
+    info "returns non-zero if there is already a datastore on HEAD."
+    info "adding the following data to the datastore of HEAD:"
+    for pair in "$@"; do
+      info "  ${pair%%=*}: ${pair#*=}\n"
+      printf "${pair%%=*}: ${pair#*=}\n"
+    done | tg_ds_add_data || die "E: HEAD already has a datastore"
+    ;;
+  remove)
+    # removes from HEAD
+    info "always returns zero, even if there was nothing to remove."
+    tg_ds_remove_data
+    ;;
+  list)
+    # $2 is the commit
+    info "returns non-zero if no datastore found at given commit."
+    info "prints contents of datastore otherwise."
+    tg_ds_list_data "${2:-HEAD}"
+    ;;
+  get)
+    # get parameter $2 from $3 (default HEAD)
+    info "prints the value of the parameter stored in the given commit."
+    info "prints nothing if the commit has a datastore but without the parameter."
+    info "returns non-zero if there is no datastore."
+    tg_ds_get_value "$2" ${3:-HEAD}
+    ;;
+  find)
+    # search for parameter $2 by backtracking from $3 (default HEAD)
+    info "prints the value of the parameter, or empty if parameter is not found."
+    info "returns non-zero if no datastore was found."
+    tg_ds_find_value "$2" ${3:-HEAD}
+    ;;
+  *)
+    echo "Usage: ${0##*/} [ add var=val... | remove | list | get var [commit] | find var [commit] ]"
+    ;;
+esac

diff --git a/tg-datastore-pcommits.inc b/tg-datastore-pcommits.inc
new file mode 100644 (file)
index 0000000..f03ede5
--- /dev/null
+++ b/tg-datastore-pcommits.inc
@@ -0,0 +1,85 @@
+_get_empty_treeref()
+{
+  git mktree </dev/null
+}
+
+_make_pcommit()
+{
+  local timestamp; timestamp=$(date +'%s %z')
+  git hash-object -t commit -w --stdin <<-_commit_data
+       tree $(_get_empty_treeref)
+       author TopGit <> $timestamp
+       committer "$author"
+       x-topgit-data-node yes
+
+       TopGit data node
+
+       This commit is used internally by TopGit. Please just ignore it.
+
+       TopGit data follow:
+       $(cat)
+       _commit_data
+}
+
+_append_parentref_to_HEAD()
+{
+  local parent; parent="$1"
+  local ref; ref=$(git cat-file commit HEAD |
+                     sed -e "/^parent/aparent ${parent}" |
+                     git hash-object -t commit -w --stdin)
+  git update-ref HEAD $ref
+}
+
+_remove_parentref_from_HEAD()
+{
+  local parent; parent="$1"
+  local ref; ref=$(git cat-file commit HEAD |
+                     grep -v "^parent ${parent}" |
+                     git hash-object -t commit -w --stdin)
+  git update-ref HEAD $ref
+}
+
+# returns 0 if $1 is a valid TopGit pcommit
+_is_pcommit()
+{
+  local pcommit; pcommit="$1"
+  git cat-file commit $pcommit | grep -q '^x-topgit-data-node yes$'
+}
+
+# returns the ref of the pcommit attached to $1
+# returns 1 when none is found
+_find_pcommit()
+{
+  local commit; commit="$1"
+  local parentnr; parentnr=1
+
+  while :; do
+    ref=$(tg_ds_resolve_commit "${commit}^${parentnr}") || break
+    _is_pcommit "$ref" && printf "$ref\n" && return 0
+    parentnr=$(($parentnr + 1))
+  done
+  return 1
+}
+
+# expects data on stdin and adds to HEAD
+tg_ds_add_data()
+{
+  local author; author=$(git cat-file commit HEAD | sed -rne 's,^author ,,p')
+  _append_parentref_to_HEAD $(_make_pcommit "$author")
+}
+
+# removes data from HEAD
+tg_ds_remove_data()
+{
+  local pcommit; pcommit=$(_find_pcommit HEAD) || return   # no error
+  _remove_parentref_from_HEAD $pcommit
+}
+
+# lists data on a given commit
+tg_ds_list_data()
+{
+  local commit; commit="${1:-HEAD}"
+  ref=$(tg_ds_resolve_commit $commit) || die "tg_ds_list_data: invalid commit: $commit"
+  local pcommit; pcommit=$(_find_pcommit $commit) || return 1
+  git cat-file commit $pcommit | sed -e '0,/^TopGit data follow:$/d'
+}

diff --git a/tg-datastore.inc b/tg-datastore.inc
new file mode 100644 (file)
index 0000000..d79f159
--- /dev/null
+++ b/tg-datastore.inc
@@ -0,0 +1,45 @@
+die()
+{
+  printf "E: $@\n" >&2
+  exit 1
+}
+
+tg_ds_resolve_commit()
+{
+  git rev-parse --verify $1 2>/dev/null
+}
+
+. ${0%/*}/tg-datastore-pcommits.inc
+
+tg_ds_get_value()
+{
+  local name; name="${1:-}"
+  local commit; commit="${2:-HEAD}"
+
+  [ -z "$1" ] && die 'tg_ds_get_value: missing first argument (name)'
+  tg_ds_resolve_commit $commit >/dev/null || die "tg_ds_get_value: invalid commit: $commit"
+
+  local data; data=$(tg_ds_list_data "$commit") || return 1
+  printf "$data\n" | sed -rne "s,^${name}: *,,p"
+}
+
+tg_ds_find_value()
+{
+  local name; name="${1:-}"
+  local commit; commit="${2:-HEAD}"
+
+  [ -z "$1" ] && die 'tg_ds_find_value: missing first argument (name)'
+  ref=$(tg_ds_resolve_commit $commit) || die "tg_ds_find_value: invalid commit: $commit"
+
+  while :; do
+    if [ "$name" = commitref ]; then
+      tg_ds_list_data "$commit" >/dev/null && printf "$ref\n" && return 0
+    else
+      tg_ds_get_value "$name" $commit && return 0
+    fi
+    commit="${commit}^"
+    ref=$(tg_ds_resolve_commit "${commit}") || break
+  done
+
+  return 1
+}