Fix bugs with gitception://<giturl> related to concurrency with git

Make sure we do not overwrite FETCH_HEAD. Using stacked gitception://
URLs was useful to make sure we handle our temporaries in a safe way.

diff --git a/git-remote-gcrypt b/git-remote-gcrypt
index 11a018d6c6c03eabf585a2aa17c3b5d3782ebcd2..5924ebe240a70ea0026e8e1a32b568fd4726d718 100755 (executable)
--- a/git-remote-gcrypt
+++ b/git-remote-gcrypt
@@ -22,7 +22,8 @@ pack_hash()
 LOCALDIR="${GIT_DIR:-.git}/remote-gcrypt"
 DID_FIND_REPO=  # yes for connected, no for no repo
 PACKPFX="pack :SHA224:"
-GREF="refs/gcrypt/togit"
+export GITCEPTION="$GITCEPTION+" # Reuse $GREF except when stacked
+GREF="refs/gcrypt/gitception.$GITCEPTION"
 
 isurl() { test -z "${2%%$1://*}" ; }
 
@@ -33,33 +34,23 @@ splitcolon()
        suffix_=${1#*:}
 }
 
-# Fetch repo $1, file $2
-GET()
+## gitception part
+# Fetch giturl $1, file $2
+gitception_get()
 {
-       local REPO
-       if isurl ssh "$1"
-       then
-               splitcolon "${1#ssh://}"
-               (exec 0>&-; ssh "$prefix_" "cat $suffix_/$2")
-       elif isurl sftp "$1"
-       then
-               (exec 0>&-; curl -s -S -k "$1/$2")
-       elif isurl gitception "$1"
-       then
-               REPO=${1#gitception://}
-               git fetch "$REPO" 2>/dev/null >&2 && \
-                       OBJID=$(git ls-tree FETCH_HEAD | xgrep -E "\b$2$" | \
-                               awk '{print $3}') && [ -n "$OBJID" ] && \
-                       git cat-file blob "$OBJID"
-               git update-ref "$GREF" FETCH_HEAD
-       else
-               cat "$1/$2"
-       fi
+       # Take care to preserve FETCH_HEAD
+       local FHEAD
+       local RETVAL
+       FHEAD="$GIT_DIR/FETCH_HEAD"
+       [ -e "$FHEAD" ] && command mv -f "$FHEAD" "$FHEAD.$$~" || :
+       git fetch -q -f "$1" HEAD:"$GREF" 2>/dev/tty >/dev/null && \
+               OBJID=$(git ls-tree "$GREF" | xgrep -E "\b$2$" |
+                       awk '{print $3}') && [ -n "$OBJID" ] && \
+               git cat-file blob "$OBJID" && RETVAL=: || \
+               { RETVAL=false && : ; }
+       [ -e "$FHEAD.$$~" ] && command mv -f "$FHEAD.$$~" "$FHEAD" && $RETVAL
 }
 
-# Fetch repo $1, file $2 or return encrypted empty message
-GET_OR_EMPTY() { GET "$@" 2>/dev/null || (printf "" | ENCRYPT) ; }
-
 anon_commit()
 {
        GIT_AUTHOR_NAME="root" GIT_AUTHOR_EMAIL="root@localhost" \
@@ -77,6 +68,38 @@ update_tree()
                printf "100644 blob %s\t%s" "$3" "$2") | git mktree
 }
 
+# Put giturl $1, file $2
+# depends on previous GET to set $GREF and depends on PUT_FINAL later
+gitception_put()
+{
+       OBJID=$(git hash-object -w --stdin) && \
+               TREEID=$(update_tree "$GREF" "$2" "$OBJID") &&
+               COMMITID=$(anon_commit "$TREEID" -m "x") && \
+               git update-ref "$GREF" "$COMMITID"
+}
+## end gitception
+
+# Fetch repo $1, file $2
+GET()
+{
+       if isurl ssh "$1"
+       then
+               splitcolon "${1#ssh://}"
+               (exec 0>&-; ssh "$prefix_" "cat $suffix_/$2")
+       elif isurl sftp "$1"
+       then
+               (exec 0>&-; curl -s -S -k "$1/$2")
+       elif isurl gitception "$1"
+       then
+               gitception_get "${1#gitception://}" "$2"
+       else
+               cat "$1/$2"
+       fi
+}
+
+# Fetch repo $1, file $2 or return encrypted empty message
+GET_OR_EMPTY() { GET "$@" 2>/dev/null || (printf "" | ENCRYPT) ; }
+
 # Put repo $1, file $2 or fail
 PUT()
 {
@@ -89,10 +112,7 @@ PUT()
                curl -s -S -k --ftp-create-dirs -T - "$1/$2"
        elif isurl gitception "$1"
        then
-               OBJID=$(git hash-object -w --stdin) && \
-                       TREEID=$(update_tree "$GREF" "$2" "$OBJID") &&
-                       COMMITID=$(anon_commit "$TREEID" -m "x") && \
-                       git update-ref "$GREF" "$COMMITID"
+               gitception_put "${1#gitception://}" "$2"
        else
                cat > "$1/$2"
        fi
@@ -101,11 +121,9 @@ PUT()
 # Put all PUT changes for repo $1 at once
 PUT_FINAL()
 {
-       local REPO
        if isurl gitception "$1"
        then
-               REPO=${1#gitception://}
-               git push --quiet -f "$REPO" "$GREF":master
+               git push --quiet -f "${1#gitception://}" "$GREF":master
        else
                :
        fi
@@ -130,6 +148,11 @@ PUTREPO()
        fi
 }
 
+CLEAN_FINAL()
+{
+       isurl gitception "$1" && git update-ref -d "$GREF" || :
+}
+
 ENCRYPT()
 {
        # Security protocol:
@@ -289,7 +312,8 @@ do_fetch()
        trap 'rm -f "$TMPPACK_ENCRYPTED"' EXIT
 
        # Needed packs is  REMOTE - (HAVE & REMOTE)
-       PHAVE="$(cat "$LOCALDIR/have_packs" 2>/dev/null || :)"
+       # The `+` for $GITCEPTION is pointless but we will be safe for stacking
+       PHAVE="$(cat "$LOCALDIR/have_packs+" 2>/dev/null || :)"
        PBOTH="$(printf "%s\n%s" "$PACKLIST" "$PHAVE" | sort_C | uniq -d)"
        PNEED="$(printf "%s\n%s" "$PACKLIST" "$PBOTH" | sort_C | uniq -u)"
 
@@ -306,7 +330,7 @@ do_fetch()
                DECRYPT < "$TMPPACK_ENCRYPTED" | \
                        git index-pack -v --stdin >/dev/null
                # add to local pack list
-               printf "$PACKPFX%s\n" "$PACK" >> "$LOCALDIR/have_packs"
+               printf "$PACKPFX%s\n" "$PACK">>"$LOCALDIR/have_packs$GITCEPTION"
        done
 
        rm -f "$TMPPACK_ENCRYPTED"
@@ -407,7 +431,7 @@ mkdir -p "$LOCALDIR"
 
 while read INPUT
 do
-       #echo_info "Got: $INPUT"
+       #echo_info "Got: $INPUT ($GITCEPTION)"
        case "$INPUT" in
        capabilities)
                do_capabilities
@@ -452,6 +476,7 @@ do
                ;;
        *)
                #echo_info "Blank line, we are done"
+               CLEAN_FINAL "$URL"
                exit 0
                ;;
        esac