contrib/git-exproll.sh - gerrit - Git at Google

 #!/bin/bash
 # Copyright (c) 2012, Code Aurora Forum. All rights reserved.
 #
 # Redistribution and use in source and binary forms, with or without
 # modification, are permitted provided that the following conditions are
 # met:
 #    # Redistributions of source code must retain the above copyright
 #       notice, this list of conditions and the following disclaimer.
 #    # Redistributions in binary form must reproduce the above
 #       copyright notice, this list of conditions and the following
 #       disclaimer in the documentation and/or other materials provided
 #       with the distribution.
 #    # Neither the name of Code Aurora Forum, Inc. nor the names of its
 #       contributors may be used to endorse or promote products derived
 #       from this software without specific prior written permission.
 #
 # THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
 # WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
 # MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
 # ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
 # BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
 # CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
 # SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
 # BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
 # WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
 # OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
 # IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

 usage() { # error_message

     cat <<-EOF
 		usage: $(basename $0) [-unvt] [--noref] [--nolosse] [-r|--ratio number]
 		                      [git gc option...] git.repo

 		-u|-h                usage/help
 		-v verbose
 		-n dry-run           don't actually repack anything
 		-t touch             treat repo as if it had been touched
 		--noref              avoid extra ref packing timestamp checking
 		--noloose            do not run just because there are loose object dirs
 		                     (repacking may still run if they are referenced)
 		-r ratio <number>    packfile ratio to aim for (default 10)

 		git gc option        will be passed as args to git gc

 		git.repo             to run gc against

 		Garbage collect using a pseudo logarithmic packfile maintenance
 		approach.  This approach attempts to minimize packfile churn
 		by keeping several generations of varying sized packfiles around
 		and only consolidating packfiles (or loose objects) which are
 		either new packfiles, or packfiles close to the same size as
 		another packfile.

 		An estimate is used to predict when rollups (one consolidation
 		would cause another consolidation) would occur so that this
 		rollup can be done all at once via a single repack.  This reduces
 		both the runtime and the pack file churn in rollup cases.

 		Approach: plan each consolidation by creating a table like this:

 		Id Keep Size           Sha1(or consolidation list)      Actions(repack down up note)
 		1     - 11356          9052edfb7392646cd4e5f362b953675985f01f96 y - - New
 		2     - 429088         010904d5c11cd26a79fda91b01ab454d1001b402 y - - New
 		c1    - 440444         [1,2]                                    - - -

 		Id:    numbers preceded by a c are estimated "c pack" files
 		Keep:  - none, k private keep, o our keep
 		Size:  in disk blocks (default du output)
 		Sha1:  of packfile, or consolidation list of packfile ids
 		Actions
 		repack: - n no, y yes
 		down:   - noop, ^ consolidate with a file above
 		up:     - noop, v consolidate with a file below
 		note:   Human description of script decisions:
 		         New (file is a new packfile)
 		         Consolidate with:<list of packfile ids>
 		         (too far from:<list of packfile ids>)

 		On the first pass, always consolidate any new packfiles along
 		with loose objects and along with any packfiles which are within
 		the ratio size of their predecessors (note, the list is ordered
 		by increasing size).  After each consolidation, insert a fake
 		consolidation, or "c pack", to naively represent the size and
 		ordered positioning of the anticipated new consolidated pack.
 		Every time a new pack is planned, rescan the list in case the
 		new "c pack" would cause more consolidation...

 		Once the packfiles which need consolidation are determined, the
 		packfiles which will not be consolidated are marked with a .keep
 		file, and those which will be consolidated will have their .keep
 		removed if they have one.  Thus, the packfiles with a .keep will
 		not get repacked.

 		Packfile consolidation is determined by the --ratio parameter
 		(default is 10).  This ratio is somewhat of a tradeoff.  The
 		smaller the number, the more packfiles will be kept on average;
 		this increases disk utilization somewhat.  However, a larger
 		ratio causes greater churn and may increase disk utilization due
 		to deleted packfiles not being reclaimed since they may still be
 		kept open by long running applications such as Gerrit.  Sane
 		ratio values are probably between 2 and 10.  Since most
 		consolidations actually end up smaller than the estimated
 		consolidated packfile size (due to compression), the true ratio
 		achieved will likely be 1 to 2 greater than the target ratio.
 		The smaller the target ratio, the greater this discrepancy.

 		Finally, attempt to skip garbage collection entirely on untouched
 		repos.  In order to determine if a repo has been touched, use the
 		timestamp on the script's keep files, if any relevant file/dir
 		is newer than a keep marker file, assume that the repo has been
 		touched and gc needs to run.  Also assume gc needs to run whenever
 		there are loose object dirs since they may contain untouched
 		unreferenced loose objects which need to be pruned (once they
 		expire).

 		In order to allow the keep files to be an effective timestamp
 		marker to detect relevant changes in a repo since the last run,
 		all relevant files and directories which may be modified during a
 		gc run (even during a noop gc run), must have their timestamps
 		reset to the same time as the keep files or gc will always run
 		even on untouched repos.  The relevant files/dirs are all those
 		files and directories which garbage collection, object packing,
 		ref packing and pruning might change during noop actions.
 EOF

     [ -n "$1" ] && info "ERROR $1"

     exit
 }

 debug() { [ -n "$SW_V" ] && info "$1" ; }
 info() { echo "$1" >&2 ; }

 array_copy() { #v2 # array_src array_dst
     local src=$1 dst=$2
     local s i=0
     eval s=\${#$src[@]}
     while [ $i -lt $s ] ; do
         eval $dst[$i]=\"\${$src[$i]}\"
         i=$(($i + 1))
     done
 }

 array_equals() { #v2 # array_name [vals...]
     local a=$1 ; shift
     local s=0 t=() val
     array_copy "$a" t
     for s in "${!t[@]}" ; do s=$((s+1)) ; done
     [ "$s" -ne "$#" ] && return 1
     for val in "${t[@]}" ; do
         [ "$val" = "$1" ] || return 2
         shift
     done
     return 0
 }

 packs_sizes() { # git.repo > "size pack"...
     du -s "$1"/objects/pack/pack-$SHA1.pack | sort -n 2> /dev/null
 }

 is_ourkeep() { grep -q "$KEEP" "$1" 2> /dev/null ; } # keep
 has_ourkeep() { is_ourkeep "$(keep_for "$1")" ; } # pack
 has_keep() { [ -f "$(keep_for "$1")" ] ; } # pack
 is_repo() { [ -d "$1/objects" ] && [ -d "$1/refs/heads" ] ; } # git.repo

 keep() { # pack   # returns true if we added our keep
     keep=$(keep_for "$1")
     [ -f "$keep" ] && return 1
     echo "$KEEP" > "$keep"
     return 0
 }

 keep_for() { # packfile > keepfile
     local keep=$(echo "$1" | sed -es'/\.pack$/.keep/')
     [ "${keep/.keep}" = "$keep" ] && return 1
     echo "$keep"
 }

 idx_for() { # packfile > idxfile
     local idx=$(echo "$1" | sed -es'/\.pack$/.idx/')
     [ "${idx/.idx}" = "$idx" ] && return 1
     echo "$idx"
 }

 # pack_or_keep_file > sha
 sha_for() { echo "$1" | sed -es'|\(.*/\)*pack-\([^.]*\)\..*$|\2|' ; }

 private_keeps() { # git.repo -> sets pkeeps
     local repo=$1 ary=$2
     local keep keeps=("$repo"/objects/pack/pack-$SHA1.keep)
     pkeeps=()
     for keep in "${keeps[@]}" ; do
         is_ourkeep "$keep" || pkeeps=("${pkeeps[@]}" "$keep")
     done
 }

 is_tooclose() { [ "$(($1 * $RATIO))" -gt "$2" ] ; } # smaller larger

 unique() { # [args...] > unique_words
     local lines=$(while [ $# -gt 0 ] ; do echo "$1" ; shift ; done)
     lines=$(echo "$lines" | sort -u)
     echo $lines  # as words
 }

 outfs() { # fs [args...] > argfs...
     local fs=$1 ; shift
     [ $# -gt 0 ] && echo -n "$1" ; shift
     while [ $# -gt 0 ] ; do echo -n "$fs$1" ; shift ; done
 }

 sort_list() { # < list > formatted_list
     # n has_keep size sha repack down up note
     awk '{ note=$8; for(i=8;i<NF;i++) note=note " "$(i+1)
            printf("%-5s %s %-14s %-40s %s %s %s %s\n", \
                      $1,$2,   $3,  $4, $5,$6,$7,note)}' |\
         sort -k 3,3n -k 1,1n
 }

 is_touched() { # git.repo
     local repo=$1
     local loose keep ours newer
     [ -n "$SW_T" ] && { debug "$SW_T -> treat as touched" ; return 0 ; }

     if [ -z "$SW_LOOSE" ] ; then
         # If there are loose objects, they may need to be pruned,
         # run even if nothing has really been touched.
         loose=$(find "$repo/objects" -type d \
                       -wholename "$repo/objects/[0-9][0-9]"
                       -print -quit 2>/dev/null)
         [ -n "$loose" ] && { info "There are loose object directories" ; return 0 ; }
     fi

     # If we don't have a keep, the current packfiles may not have been
     # compressed with the current gc policy (gc may never have been run),
     # so run at least once to repack everything.  Also, we need a marker
     # file for timestamp tracking (a dir needs to detect changes within
     # it, so it cannot be a marker) and our keeps are something we control,
     # use them.
     for keep in "$repo"/objects/pack/pack-$SHA1.keep ; do
         is_ourkeep "$keep" && { ours=$keep ; break ; }
     done
     [ -z "$ours" ] && { info 'We have no keep (we have never run?): run' ; return 0 ; }

     debug "Our timestamp keep: $ours"
     # The wholename stuff seems to get touched by a noop git gc
     newer=$(find "$repo/objects" "$repo/refs" "$repo/packed-refs" \
                   '!' -wholename "$repo/objects/info" \
                   '!' -wholename "$repo/objects/info/*" \
                   -newer "$ours" \
                   -print -quit 2>/dev/null)
     [ -z "$newer" ] && return 1

     info "Touched since last run: $newer"
     return 0
 }

 touch_refs() { # git.repo start_date refs
     local repo=$1 start_date=$2 refs=$3
     (
         debug "Setting start date($start_date) on unpacked refs:"
         debug "$refs"
         cd "$repo/refs" || return
         # safe to assume no newlines in a ref name
         echo "$refs" | xargs -d '\n' -n 1 touch -c -d "$start_date"
     )
 }

 set_start_date() { # git.repo start_date refs refdirs packedrefs [packs]
     local repo=$1 start_date=$2 refs=$3 refdirs=$4 packedrefs=$5 ; shift 5
     local pack keep idx repacked

     # This stuff is touched during object packs
     while [ $# -gt 0 ] ; do
         pack=$1 ; shift
         keep="$(keep_for "$pack")"
         idx="$(idx_for "$pack")"
         touch -c -d "$start_date" "$pack" "$keep" "$idx"
         debug "Setting start date on: $pack $keep $idx"
     done
     # This will prevent us from detecting any deletes in the pack dir
     # since gc ran, except for private keeps which we are checking
     # manually.  But there really shouldn't be any other relevant deletes
     # in this dir which should cause us to rerun next time, deleting a
     # pack or index file by anything but gc would be bad!
     debug "Setting start date on pack dir: $start_date"
     touch -c -d "$start_date" "$repo/objects/pack"


     if [ -z "$SW_REFS" ] ; then
         repacked=$(find "$repo/packed-refs" -newer "$repo/objects/pack"
                       -print -quit 2>/dev/null)
         if [ -n "$repacked" ] ; then
             # The ref dirs and packed-ref files seem to get touched even on
             # a noop refpacking
             debug "Setting start date on packed-refs"
             touch -c -d "$start_date" "$repo/packed-refs"
             touch_refs "$repo" "$start_date" "$refdirs"

             # A ref repack does not imply a ref change, but since it is
             # hard to tell, simply assume so
             if [ "$refs" != "$(cd "$repo/refs" ; find -depth)" ] || \
                [ "$packedrefs" != "$(<"$repo/packed-refs")" ] ; then
                 # We retouch if needed (instead of simply checking then
                 # touching) to avoid a race between the check and the set.
                 debug "  but refs actually got packed, so retouch packed-refs"
                 touch -c "$repo/packed-refs"
             fi
         fi
     fi
 }

 note_consolidate() { # note entry > note (no duplicated consolidated entries)
     local note=$1 entry=$2
     local entries=() ifs=$IFS
     if  echo "$note" | grep -q 'Consolidate with:[0-9,c]' ; then
         IFS=,
         entries=( $(echo "$note" | sed -es'/^.*Consolidate with:\([0-9,c]*\).*$/\1/') )
         note=( $(echo "$note" | sed -es'/Consolidate with:[0-9,c]*//') )
         IFS=$ifs
     fi
     entries=( $(unique "${entries[@]}" "$entry") )
     echo "$note Consolidate with:$(outfs , "${entries[@]}")"
 }

 note_toofar() { # note entry > note (no duplicated "too far" entries)
     local note=$1 entry=$2
     local entries=() ifs=$IFS
     if  echo "$note" | grep -q '(too far from:[0-9,c]*)' ; then
         IFS=,
         entries=( $(echo "$note" | sed -es'/^.*(too far from:\([0-9,c]*\)).*$/\1/') )
         note=( $(echo "$note" | sed -es'/(too far from:[0-9,c]*)//') )
         IFS=$ifs
     fi
     entries=( $(unique "${entries[@]}" "$entry") )
     echo "$note (too far from:$(outfs , "${entries[@]}"))"
 }

 last_entry() { # isRepack pline repackline > last_rows_entry
     local size_hit=$1 pline=$2 repackline=$3
     if [ -n "$pline" ] ; then
         if [ -n "$size_hit" ] ; then
             echo "$repack_line"
         else
             echo "$pline"
         fi
     fi
 }

 init_list() { # git.repo > shortlist
     local repo=$1
     local file
     local n has_keep size sha repack

     packs_sizes "$1" | {
         while read size file ; do
             n=$((n+1))
             repack=n
             has_keep=-
             if has_keep "$file" ; then
                 has_keep=k
                 has_ourkeep "$file" && has_keep=o
             fi
             sha=$(sha_for "$file")
             echo "$n $has_keep $size $sha $repack"
         done
     } | sort_list
 }

 consolidate_list() { # run < list > list
     local run=$1
     local sum=0 psize=0 sum_size=0 size_hit pn clist pline repackline
     local n has_keep size sha repack down up note

     {
         while read n has_keep size sha repack down up note; do
             [ -z "$up" ] && up='-'
             [ -z "$down" ] && down="-"

             if [ "$has_keep" = "k" ] ; then
                 echo "$n $has_keep $size $sha $repack - - Private"
                 continue
             fi

             if [ "$repack" = "n" ] ; then
                 if is_tooclose $psize $size ; then
                     size_hit=y
                     repack=y
                     sum=$(($sum + $sum_size + $size))
                     sum_size=0 # Prevents double summing this entry
                     clist=($(unique "${clist[@]}" $pn $n))
                     down="^"
                     [ "$has_keep" = "-" ] && note="$note New +"
                     note=$(note_consolidate "$note" "$pn")
                 elif [ "$has_keep" = "-" ] ; then
                     repack=y
                     sum=$(($sum + $size))
                     sum_size=0 # Prevents double summing this entry
                     clist=($(unique "${clist[@]}" $n))
                     note="$note New"
                 elif [ $psize -ne 0 ] ; then
                     sum_size=$size
                     down="!"
                     note=$(note_toofar "$note" "$pn")
                 else
                     sum_size=$size
                 fi
             else
                 sum_size=$size
             fi

             # By preventing "c files" (consolidated) from being marked
             # "repack" they won't get keeps
             repack2=y
             [ "${n/c}" != "$n" ] && { repack=- ; repack2=- ; }

             last_entry "$size_hit" "$pline" "$repack_line"
             # Delay the printout until we know whether we are
             # being consolidated with the entry following us
             # (we won't know until the next iteration).
             # size_hit is used to determine which of the lines
             # below will actually get printed above on the next
             # iteration.
             pline="$n $has_keep $size $sha $repack $down $up $note"
             repack_line="$n $has_keep $size $sha $repack2 $down v $note"

             pn=$n ; psize=$size # previous entry data
             size_hit='' # will not be consolidated up

         done
         last_entry "$size_hit" "$pline" "$repack_line"

         [ $sum -gt 0 ] && echo "c$run - $sum [$(outfs , "${clist[@]}")] - - -"

     } | sort_list
 }

 process_list() { # git.repo > list
     local list=$(init_list "$1")  plist run=0

     while true ; do
         plist=$list
         run=$((run +1))
         list=$(echo "$list" | consolidate_list "$run")
         if [ "$plist" != "$list" ] ; then
             debug "------------------------------------------------------------------------------------"
             debug "$HEADER"
             debug "$list"
         else
             break
         fi
     done
     debug "------------------------------------------------------------------------------------"
     echo "$list"
 }

 repack_list() { # git.repo < list
     local repo=$1
     local start_date newpacks=0 pkeeps keeps=1 refs refdirs rtn
     local packedrefs=$(<"$repo/packed-refs")

     # so they don't appear touched after a noop refpacking
     if [ -z "$SW_REFS" ] ; then
         refs=$(cd "$repo/refs" ; find -depth)
         refdirs=$(cd "$repo/refs" ; find -type d -depth)
         debug "Before refs:"
         debug "$refs"
     fi

     # Find a private keep snapshot which has not changed from
     # before our start_date so private keep deletions during gc
     # can be detected
     while ! array_equals pkeeps "${keeps[@]}" ; do
        debug "Getting a private keep snapshot"
        private_keeps "$repo"
        keeps=("${pkeeps[@]}")
        debug "before keeps: ${keeps[*]}"
        start_date=$(date)
        private_keeps "$repo"
        debug "after keeps: ${pkeeps[*]}"
     done

     while read n has_keep size sha repack down up note; do
         if [ "$repack" = "y" ] ; then
             keep="$repo/objects/pack/pack-$sha.keep"
             info "Repacking $repo/objects/pack/pack-$sha.pack"
             [ -f "$keep" ] && rm -f "$keep"
         fi
     done

     ( cd "$repo" && git gc "${GC_OPTS[@]}" ) ; rtn=$?

     # Mark any files withoug a .keep with our .keep
     packs=("$repo"/objects/pack/pack-$SHA1.pack)
     for pack in "${packs[@]}" ; do
         if keep "$pack" ; then
             info "New pack: $pack"
             newpacks=$((newpacks+1))
         fi
     done

     # Record start_time.  If there is more than 1 new packfile, we
     # don't want to risk touching it with an older date since that
     # would prevent consolidation on the next run.  If the private
     # keeps have changed, then we should run next time no matter what.
     if [ $newpacks -le 1 ] || ! array_equals pkeeps "${keeps[@]}" ; then
         set_start_date "$repo" "$start_date" "$refs" "$refdirs" "$packedrefs" "${packs[@]}"
     fi

     return $rtn # we really only care about the gc error code
 }

 git_gc() { # git.repo
     local list=$(process_list "$1")
     if [ -z "$SW_V" ] ; then
         info "Running $PROG on $1.  git gc options: ${GC_OPTS[@]}"
         echo "$HEADER" >&2
         echo "$list" >&2 ;
     fi
     echo "$list" | repack_list "$1"
 }


 PROG=$(basename "$0")
 HEADER="Id Keep Size           Sha1(or consolidation list)      Actions(repack down up note)"
 KEEP=git-exproll
 HEX='[0-9a-f]'
 HEX10=$HEX$HEX$HEX$HEX$HEX$HEX$HEX$HEX$HEX$HEX
 SHA1=$HEX10$HEX10$HEX10$HEX10

 RATIO=10
 SW_N='' ; SW_V='' ; SW_T='' ; SW_REFS='' ; SW_LOOSE='' ; GC_OPTS=()
 while [ $# -gt 0 ] ; do
     case "$1" in
         -u|-h)  usage ;;
         -n)  SW_N="$1" ;;
         -v)  SW_V="$1" ;;

         -t)  SW_T="$1" ;;
         --norefs)  SW_REFS="$1" ;;
         --noloose) SW_LOOSE="$1" ;;

         -r|--ratio)  shift ; RATIO="$1" ;;

         *)  [ $# -le 1 ] && break
             GC_OPTS=( "${GC_OPTS[@]}" "$1" )
             ;;
     esac
     shift
 done


 REPO="$1"
 if ! is_repo "$REPO" ; then
     REPO=$REPO/.git
     is_repo "$REPO" || usage "($1) is not likely a git repo"
 fi


 if [ -z "$SW_N" ] ; then
     is_touched "$REPO" || { info "Repo untouched since last run" ; exit ; }
     git_gc "$REPO"
 else
     is_touched "$REPO" || info "Repo untouched since last run, analyze anyway."
     process_list "$REPO" >&2
 fi
	#!/bin/bash
	# Copyright (c) 2012, Code Aurora Forum. All rights reserved.
	#
	# Redistribution and use in source and binary forms, with or without
	# modification, are permitted provided that the following conditions are
	# met:
	# # Redistributions of source code must retain the above copyright
	# notice, this list of conditions and the following disclaimer.
	# # Redistributions in binary form must reproduce the above
	# copyright notice, this list of conditions and the following
	# disclaimer in the documentation and/or other materials provided
	# with the distribution.
	# # Neither the name of Code Aurora Forum, Inc. nor the names of its
	# contributors may be used to endorse or promote products derived
	# from this software without specific prior written permission.
	#
	# THIS SOFTWARE IS PROVIDED "AS IS" AND ANY EXPRESS OR IMPLIED
	# WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
	# MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT
	# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS
	# BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
	# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
	# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
	# BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY,
	# WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE
	# OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN
	# IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.

	usage() { # error_message

	cat <<-EOF
	usage: $(basename $0) [-unvt] [--noref] [--nolosse] [-r\|--ratio number]
	[git gc option...] git.repo

	-u\|-h usage/help
	-v verbose
	-n dry-run don't actually repack anything
	-t touch treat repo as if it had been touched
	--noref avoid extra ref packing timestamp checking
	--noloose do not run just because there are loose object dirs
	(repacking may still run if they are referenced)
	-r ratio <number> packfile ratio to aim for (default 10)

	git gc option will be passed as args to git gc

	git.repo to run gc against

	Garbage collect using a pseudo logarithmic packfile maintenance
	approach. This approach attempts to minimize packfile churn
	by keeping several generations of varying sized packfiles around
	and only consolidating packfiles (or loose objects) which are
	either new packfiles, or packfiles close to the same size as
	another packfile.

	An estimate is used to predict when rollups (one consolidation
	would cause another consolidation) would occur so that this
	rollup can be done all at once via a single repack. This reduces
	both the runtime and the pack file churn in rollup cases.

	Approach: plan each consolidation by creating a table like this:

	Id Keep Size Sha1(or consolidation list) Actions(repack down up note)
	1 - 11356 9052edfb7392646cd4e5f362b953675985f01f96 y - - New
	2 - 429088 010904d5c11cd26a79fda91b01ab454d1001b402 y - - New
	c1 - 440444 [1,2] - - -

	Id: numbers preceded by a c are estimated "c pack" files
	Keep: - none, k private keep, o our keep
	Size: in disk blocks (default du output)
	Sha1: of packfile, or consolidation list of packfile ids
	Actions
	repack: - n no, y yes
	down: - noop, ^ consolidate with a file above
	up: - noop, v consolidate with a file below
	note: Human description of script decisions:
	New (file is a new packfile)
	Consolidate with:<list of packfile ids>
	(too far from:<list of packfile ids>)

	On the first pass, always consolidate any new packfiles along
	with loose objects and along with any packfiles which are within
	the ratio size of their predecessors (note, the list is ordered
	by increasing size). After each consolidation, insert a fake
	consolidation, or "c pack", to naively represent the size and
	ordered positioning of the anticipated new consolidated pack.
	Every time a new pack is planned, rescan the list in case the
	new "c pack" would cause more consolidation...

	Once the packfiles which need consolidation are determined, the
	packfiles which will not be consolidated are marked with a .keep
	file, and those which will be consolidated will have their .keep
	removed if they have one. Thus, the packfiles with a .keep will
	not get repacked.

	Packfile consolidation is determined by the --ratio parameter
	(default is 10). This ratio is somewhat of a tradeoff. The
	smaller the number, the more packfiles will be kept on average;
	this increases disk utilization somewhat. However, a larger
	ratio causes greater churn and may increase disk utilization due
	to deleted packfiles not being reclaimed since they may still be
	kept open by long running applications such as Gerrit. Sane
	ratio values are probably between 2 and 10. Since most
	consolidations actually end up smaller than the estimated
	consolidated packfile size (due to compression), the true ratio
	achieved will likely be 1 to 2 greater than the target ratio.
	The smaller the target ratio, the greater this discrepancy.

	Finally, attempt to skip garbage collection entirely on untouched
	repos. In order to determine if a repo has been touched, use the
	timestamp on the script's keep files, if any relevant file/dir
	is newer than a keep marker file, assume that the repo has been
	touched and gc needs to run. Also assume gc needs to run whenever
	there are loose object dirs since they may contain untouched
	unreferenced loose objects which need to be pruned (once they
	expire).

	In order to allow the keep files to be an effective timestamp
	marker to detect relevant changes in a repo since the last run,
	all relevant files and directories which may be modified during a
	gc run (even during a noop gc run), must have their timestamps
	reset to the same time as the keep files or gc will always run
	even on untouched repos. The relevant files/dirs are all those
	files and directories which garbage collection, object packing,
	ref packing and pruning might change during noop actions.
	EOF

	[ -n "$1" ] && info "ERROR $1"

	exit
	}

	debug() { [ -n "$SW_V" ] && info "$1" ; }
	info() { echo "$1" >&2 ; }

	array_copy() { #v2 # array_src array_dst
	local src=$1 dst=$2
	local s i=0
	eval s=\${#$src[@]}
	while [ $i -lt $s ] ; do
	eval $dst[$i]=\"\${$src[$i]}\"
	i=$(($i + 1))
	done
	}

	array_equals() { #v2 # array_name [vals...]
	local a=$1 ; shift
	local s=0 t=() val
	array_copy "$a" t
	for s in "${!t[@]}" ; do s=$((s+1)) ; done
	[ "$s" -ne "$#" ] && return 1
	for val in "${t[@]}" ; do
	[ "$val" = "$1" ] \|\| return 2
	shift
	done
	return 0
	}

	packs_sizes() { # git.repo > "size pack"...
	du -s "$1"/objects/pack/pack-$SHA1.pack \| sort -n 2> /dev/null
	}

	is_ourkeep() { grep -q "$KEEP" "$1" 2> /dev/null ; } # keep
	has_ourkeep() { is_ourkeep "$(keep_for "$1")" ; } # pack
	has_keep() { [ -f "$(keep_for "$1")" ] ; } # pack
	is_repo() { [ -d "$1/objects" ] && [ -d "$1/refs/heads" ] ; } # git.repo

	keep() { # pack # returns true if we added our keep
	keep=$(keep_for "$1")
	[ -f "$keep" ] && return 1
	echo "$KEEP" > "$keep"
	return 0
	}

	keep_for() { # packfile > keepfile
	local keep=$(echo "$1" \| sed -es'/\.pack$/.keep/')
	[ "${keep/.keep}" = "$keep" ] && return 1
	echo "$keep"
	}

	idx_for() { # packfile > idxfile
	local idx=$(echo "$1" \| sed -es'/\.pack$/.idx/')
	[ "${idx/.idx}" = "$idx" ] && return 1
	echo "$idx"
	}

	# pack_or_keep_file > sha
	sha_for() { echo "$1" \| sed -es'\|\(./\)pack-\([^.]\)\..$\|\2\|' ; }

	private_keeps() { # git.repo -> sets pkeeps
	local repo=$1 ary=$2
	local keep keeps=("$repo"/objects/pack/pack-$SHA1.keep)
	pkeeps=()
	for keep in "${keeps[@]}" ; do
	is_ourkeep "$keep" \|\| pkeeps=("${pkeeps[@]}" "$keep")
	done
	}

	is_tooclose() { [ "$(($1 * $RATIO))" -gt "$2" ] ; } # smaller larger

	unique() { # [args...] > unique_words
	local lines=$(while [ $# -gt 0 ] ; do echo "$1" ; shift ; done)
	lines=$(echo "$lines" \| sort -u)
	echo $lines # as words
	}

	outfs() { # fs [args...] > argfs...
	local fs=$1 ; shift
	[ $# -gt 0 ] && echo -n "$1" ; shift
	while [ $# -gt 0 ] ; do echo -n "$fs$1" ; shift ; done
	}

	sort_list() { # < list > formatted_list
	# n has_keep size sha repack down up note
	awk '{ note=$8; for(i=8;i<NF;i++) note=note " "$(i+1)
	printf("%-5s %s %-14s %-40s %s %s %s %s\n", \
	$1,$2, $3, $4, $5,$6,$7,note)}' \|\
	sort -k 3,3n -k 1,1n
	}

	is_touched() { # git.repo
	local repo=$1
	local loose keep ours newer
	[ -n "$SW_T" ] && { debug "$SW_T -> treat as touched" ; return 0 ; }

	if [ -z "$SW_LOOSE" ] ; then
	# If there are loose objects, they may need to be pruned,
	# run even if nothing has really been touched.
	loose=$(find "$repo/objects" -type d \
	-wholename "$repo/objects/[0-9][0-9]"
	-print -quit 2>/dev/null)
	[ -n "$loose" ] && { info "There are loose object directories" ; return 0 ; }
	fi

	# If we don't have a keep, the current packfiles may not have been
	# compressed with the current gc policy (gc may never have been run),
	# so run at least once to repack everything. Also, we need a marker
	# file for timestamp tracking (a dir needs to detect changes within
	# it, so it cannot be a marker) and our keeps are something we control,
	# use them.
	for keep in "$repo"/objects/pack/pack-$SHA1.keep ; do
	is_ourkeep "$keep" && { ours=$keep ; break ; }
	done
	[ -z "$ours" ] && { info 'We have no keep (we have never run?): run' ; return 0 ; }

	debug "Our timestamp keep: $ours"
	# The wholename stuff seems to get touched by a noop git gc
	newer=$(find "$repo/objects" "$repo/refs" "$repo/packed-refs" \
	'!' -wholename "$repo/objects/info" \
	'!' -wholename "$repo/objects/info/*" \
	-newer "$ours" \
	-print -quit 2>/dev/null)
	[ -z "$newer" ] && return 1

	info "Touched since last run: $newer"
	return 0
	}

	touch_refs() { # git.repo start_date refs
	local repo=$1 start_date=$2 refs=$3
	(
	debug "Setting start date($start_date) on unpacked refs:"
	debug "$refs"
	cd "$repo/refs" \|\| return
	# safe to assume no newlines in a ref name
	echo "$refs" \| xargs -d '\n' -n 1 touch -c -d "$start_date"
	)
	}

	set_start_date() { # git.repo start_date refs refdirs packedrefs [packs]
	local repo=$1 start_date=$2 refs=$3 refdirs=$4 packedrefs=$5 ; shift 5
	local pack keep idx repacked

	# This stuff is touched during object packs
	while [ $# -gt 0 ] ; do
	pack=$1 ; shift
	keep="$(keep_for "$pack")"
	idx="$(idx_for "$pack")"
	touch -c -d "$start_date" "$pack" "$keep" "$idx"
	debug "Setting start date on: $pack $keep $idx"
	done
	# This will prevent us from detecting any deletes in the pack dir
	# since gc ran, except for private keeps which we are checking
	# manually. But there really shouldn't be any other relevant deletes
	# in this dir which should cause us to rerun next time, deleting a
	# pack or index file by anything but gc would be bad!
	debug "Setting start date on pack dir: $start_date"
	touch -c -d "$start_date" "$repo/objects/pack"


	if [ -z "$SW_REFS" ] ; then
	repacked=$(find "$repo/packed-refs" -newer "$repo/objects/pack"
	-print -quit 2>/dev/null)
	if [ -n "$repacked" ] ; then
	# The ref dirs and packed-ref files seem to get touched even on
	# a noop refpacking
	debug "Setting start date on packed-refs"
	touch -c -d "$start_date" "$repo/packed-refs"
	touch_refs "$repo" "$start_date" "$refdirs"

	# A ref repack does not imply a ref change, but since it is
	# hard to tell, simply assume so
	if [ "$refs" != "$(cd "$repo/refs" ; find -depth)" ] \|\| \
	[ "$packedrefs" != "$(<"$repo/packed-refs")" ] ; then
	# We retouch if needed (instead of simply checking then
	# touching) to avoid a race between the check and the set.
	debug " but refs actually got packed, so retouch packed-refs"
	touch -c "$repo/packed-refs"
	fi
	fi
	fi
	}

	note_consolidate() { # note entry > note (no duplicated consolidated entries)
	local note=$1 entry=$2
	local entries=() ifs=$IFS
	if echo "$note" \| grep -q 'Consolidate with:[0-9,c]' ; then
	IFS=,
	entries=( $(echo "$note" \| sed -es'/^.Consolidate with:\([0-9,c]\).*$/\1/') )
	note=( $(echo "$note" \| sed -es'/Consolidate with:[0-9,c]*//') )
	IFS=$ifs
	fi
	entries=( $(unique "${entries[@]}" "$entry") )
	echo "$note Consolidate with:$(outfs , "${entries[@]}")"
	}

	note_toofar() { # note entry > note (no duplicated "too far" entries)
	local note=$1 entry=$2
	local entries=() ifs=$IFS
	if echo "$note" \| grep -q '(too far from:[0-9,c]*)' ; then
	IFS=,
	entries=( $(echo "$note" \| sed -es'/^.(too far from:\([0-9,c]\)).*$/\1/') )
	note=( $(echo "$note" \| sed -es'/(too far from:[0-9,c]*)//') )
	IFS=$ifs
	fi
	entries=( $(unique "${entries[@]}" "$entry") )
	echo "$note (too far from:$(outfs , "${entries[@]}"))"
	}

	last_entry() { # isRepack pline repackline > last_rows_entry
	local size_hit=$1 pline=$2 repackline=$3
	if [ -n "$pline" ] ; then
	if [ -n "$size_hit" ] ; then
	echo "$repack_line"
	else
	echo "$pline"
	fi
	fi
	}

	init_list() { # git.repo > shortlist
	local repo=$1
	local file
	local n has_keep size sha repack

	packs_sizes "$1" \| {
	while read size file ; do
	n=$((n+1))
	repack=n
	has_keep=-
	if has_keep "$file" ; then
	has_keep=k
	has_ourkeep "$file" && has_keep=o
	fi
	sha=$(sha_for "$file")
	echo "$n $has_keep $size $sha $repack"
	done
	} \| sort_list
	}

	consolidate_list() { # run < list > list
	local run=$1
	local sum=0 psize=0 sum_size=0 size_hit pn clist pline repackline
	local n has_keep size sha repack down up note

	{
	while read n has_keep size sha repack down up note; do
	[ -z "$up" ] && up='-'
	[ -z "$down" ] && down="-"

	if [ "$has_keep" = "k" ] ; then
	echo "$n $has_keep $size $sha $repack - - Private"
	continue
	fi

	if [ "$repack" = "n" ] ; then
	if is_tooclose $psize $size ; then
	size_hit=y
	repack=y
	sum=$(($sum + $sum_size + $size))
	sum_size=0 # Prevents double summing this entry
	clist=($(unique "${clist[@]}" $pn $n))
	down="^"
	[ "$has_keep" = "-" ] && note="$note New +"
	note=$(note_consolidate "$note" "$pn")
	elif [ "$has_keep" = "-" ] ; then
	repack=y
	sum=$(($sum + $size))
	sum_size=0 # Prevents double summing this entry
	clist=($(unique "${clist[@]}" $n))
	note="$note New"
	elif [ $psize -ne 0 ] ; then
	sum_size=$size
	down="!"
	note=$(note_toofar "$note" "$pn")
	else
	sum_size=$size
	fi
	else
	sum_size=$size
	fi

	# By preventing "c files" (consolidated) from being marked
	# "repack" they won't get keeps
	repack2=y
	[ "${n/c}" != "$n" ] && { repack=- ; repack2=- ; }

	last_entry "$size_hit" "$pline" "$repack_line"
	# Delay the printout until we know whether we are
	# being consolidated with the entry following us
	# (we won't know until the next iteration).
	# size_hit is used to determine which of the lines
	# below will actually get printed above on the next
	# iteration.
	pline="$n $has_keep $size $sha $repack $down $up $note"
	repack_line="$n $has_keep $size $sha $repack2 $down v $note"

	pn=$n ; psize=$size # previous entry data
	size_hit='' # will not be consolidated up

	done
	last_entry "$size_hit" "$pline" "$repack_line"

	[ $sum -gt 0 ] && echo "c$run - $sum [$(outfs , "${clist[@]}")] - - -"

	} \| sort_list
	}

	process_list() { # git.repo > list
	local list=$(init_list "$1") plist run=0

	while true ; do
	plist=$list
	run=$((run +1))
	list=$(echo "$list" \| consolidate_list "$run")
	if [ "$plist" != "$list" ] ; then
	debug "------------------------------------------------------------------------------------"
	debug "$HEADER"
	debug "$list"
	else
	break
	fi
	done
	debug "------------------------------------------------------------------------------------"
	echo "$list"
	}

	repack_list() { # git.repo < list
	local repo=$1
	local start_date newpacks=0 pkeeps keeps=1 refs refdirs rtn
	local packedrefs=$(<"$repo/packed-refs")

	# so they don't appear touched after a noop refpacking
	if [ -z "$SW_REFS" ] ; then
	refs=$(cd "$repo/refs" ; find -depth)
	refdirs=$(cd "$repo/refs" ; find -type d -depth)
	debug "Before refs:"
	debug "$refs"
	fi

	# Find a private keep snapshot which has not changed from
	# before our start_date so private keep deletions during gc
	# can be detected
	while ! array_equals pkeeps "${keeps[@]}" ; do
	debug "Getting a private keep snapshot"
	private_keeps "$repo"
	keeps=("${pkeeps[@]}")
	debug "before keeps: ${keeps[*]}"
	start_date=$(date)
	private_keeps "$repo"
	debug "after keeps: ${pkeeps[*]}"
	done

	while read n has_keep size sha repack down up note; do
	if [ "$repack" = "y" ] ; then
	keep="$repo/objects/pack/pack-$sha.keep"
	info "Repacking $repo/objects/pack/pack-$sha.pack"
	[ -f "$keep" ] && rm -f "$keep"
	fi
	done

	( cd "$repo" && git gc "${GC_OPTS[@]}" ) ; rtn=$?

	# Mark any files withoug a .keep with our .keep
	packs=("$repo"/objects/pack/pack-$SHA1.pack)
	for pack in "${packs[@]}" ; do
	if keep "$pack" ; then
	info "New pack: $pack"
	newpacks=$((newpacks+1))
	fi
	done

	# Record start_time. If there is more than 1 new packfile, we
	# don't want to risk touching it with an older date since that
	# would prevent consolidation on the next run. If the private
	# keeps have changed, then we should run next time no matter what.
	if [ $newpacks -le 1 ] \|\| ! array_equals pkeeps "${keeps[@]}" ; then
	set_start_date "$repo" "$start_date" "$refs" "$refdirs" "$packedrefs" "${packs[@]}"
	fi

	return $rtn # we really only care about the gc error code
	}

	git_gc() { # git.repo
	local list=$(process_list "$1")
	if [ -z "$SW_V" ] ; then
	info "Running $PROG on $1. git gc options: ${GC_OPTS[@]}"
	echo "$HEADER" >&2
	echo "$list" >&2 ;
	fi
	echo "$list" \| repack_list "$1"
	}


	PROG=$(basename "$0")
	HEADER="Id Keep Size Sha1(or consolidation list) Actions(repack down up note)"
	KEEP=git-exproll
	HEX='[0-9a-f]'
	HEX10=$HEX$HEX$HEX$HEX$HEX$HEX$HEX$HEX$HEX$HEX
	SHA1=$HEX10$HEX10$HEX10$HEX10

	RATIO=10
	SW_N='' ; SW_V='' ; SW_T='' ; SW_REFS='' ; SW_LOOSE='' ; GC_OPTS=()
	while [ $# -gt 0 ] ; do
	case "$1" in
	-u\|-h) usage ;;
	-n) SW_N="$1" ;;
	-v) SW_V="$1" ;;

	-t) SW_T="$1" ;;
	--norefs) SW_REFS="$1" ;;
	--noloose) SW_LOOSE="$1" ;;

	-r\|--ratio) shift ; RATIO="$1" ;;

	*) [ $# -le 1 ] && break
	GC_OPTS=( "${GC_OPTS[@]}" "$1" )
	;;
	esac
	shift
	done


	REPO="$1"
	if ! is_repo "$REPO" ; then
	REPO=$REPO/.git
	is_repo "$REPO" \|\| usage "($1) is not likely a git repo"
	fi


	if [ -z "$SW_N" ] ; then
	is_touched "$REPO" \|\| { info "Repo untouched since last run" ; exit ; }
	git_gc "$REPO"
	else
	is_touched "$REPO" \|\| info "Repo untouched since last run, analyze anyway."
	process_list "$REPO" >&2
	fi