submodule--helper: run update procedures from C

Add a new submodule--helper subcommand `run-update-procedure` that runs
the update procedure if the SHA1 of the submodule does not match what
the superproject expects.

This is an intermediate change that works towards total conversion of
`submodule update` from shell to C.

Specific error codes are returned so that the shell script calling the
subcommand can take a decision on the control flow, and preserve the
error messages across subsequent recursive calls of `cmd_update`.

This change is more focused on doing a faithful conversion, so for now we
are not too concerned with trying to reduce subprocess spawns.

Mentored-by: Christian Couder <christian.couder@gmail.com>
Mentored-by: Shourya Shukla <periperidip@gmail.com>
Signed-off-by: Atharva Raykar <raykar.ath@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 33 insertions, 73 deletions

diff --git a/git-submodule.sh b/git-submodule.sh
index dbd2ec2050..f703cddce8 100755
--- a/git-submodule.sh
+++ b/git-submodule.sh
@@ -369,13 +369,6 @@ cmd_deinit()
 	git ${wt_prefix:+-C "$wt_prefix"} submodule--helper deinit ${GIT_QUIET:+--quiet} ${force:+--force} ${deinit_all:+--all} -- "$@"
 }
 
-is_tip_reachable () (
-	sanitize_submodule_env &&
-	cd "$1" &&
-	rev=$(git rev-list -n 1 "$2" --not --all 2>/dev/null) &&
-	test -z "$rev"
-)
-
 # usage: fetch_in_submodule <module_path> [<depth>] [<sha1>]
 # Because arguments are positional, use an empty string to omit <depth>
 # but include <sha1>.
@@ -519,14 +512,13 @@ cmd_update()
 
 		git submodule--helper ensure-core-worktree "$sm_path" || exit 1
 
-		update_module=$(git submodule--helper update-module-mode $just_cloned "$sm_path" $update)
-
 		displaypath=$(git submodule--helper relative-path "$prefix$sm_path" "$wt_prefix")
 
 		if test $just_cloned -eq 1
 		then
 			subsha1=
 		else
+			just_cloned=
 			subsha1=$(sanitize_submodule_env; cd "$sm_path" &&
 				git rev-parse --verify HEAD) ||
 			die "fatal: $(eval_gettext "Unable to find current revision in submodule path '\$displaypath'")"
@@ -547,70 +539,38 @@ cmd_update()
 			die "fatal: $(eval_gettext "Unable to find current \${remote_name}/\${branch} revision in submodule path '\$sm_path'")"
 		fi
 
-		if test "$subsha1" != "$sha1" || test -n "$force"
-		then
-			subforce=$force
-			# If we don't already have a -f flag and the submodule has never been checked out
-			if test -z "$subsha1" && test -z "$force"
-			then
-				subforce="-f"
-			fi
-
-			if test -z "$nofetch"
-			then
-				# Run fetch only if $sha1 isn't present or it
-				# is not reachable from a ref.
-				is_tip_reachable "$sm_path" "$sha1" ||
-				fetch_in_submodule "$sm_path" $depth ||
-				say "$(eval_gettext "Unable to fetch in submodule path '\$displaypath'; trying to directly fetch \$sha1:")"
-
-				# Now we tried the usual fetch, but $sha1 may
-				# not be reachable from any of the refs
-				is_tip_reachable "$sm_path" "$sha1" ||
-				fetch_in_submodule "$sm_path" "$depth" "$sha1" ||
-				die "fatal: $(eval_gettext "Fetched in submodule path '\$displaypath', but it did not contain \$sha1. Direct fetching of that commit failed.")"
-			fi
-
-			must_die_on_failure=
-			case "$update_module" in
-			checkout)
-				command="git checkout $subforce -q"
-				die_msg="fatal: $(eval_gettext "Unable to checkout '\$sha1' in submodule path '\$displaypath'")"
-				say_msg="$(eval_gettext "Submodule path '\$displaypath': checked out '\$sha1'")"
-				;;
-			rebase)
-				command="git rebase ${GIT_QUIET:+--quiet}"
-				die_msg="fatal: $(eval_gettext "Unable to rebase '\$sha1' in submodule path '\$displaypath'")"
-				say_msg="$(eval_gettext "Submodule path '\$displaypath': rebased into '\$sha1'")"
-				must_die_on_failure=yes
-				;;
-			merge)
-				command="git merge ${GIT_QUIET:+--quiet}"
-				die_msg="fatal: $(eval_gettext "Unable to merge '\$sha1' in submodule path '\$displaypath'")"
-				say_msg="$(eval_gettext "Submodule path '\$displaypath': merged in '\$sha1'")"
-				must_die_on_failure=yes
-				;;
-			!*)
-				command="${update_module#!}"
-				die_msg="fatal: $(eval_gettext "Execution of '\$command \$sha1' failed in submodule path '\$displaypath'")"
-				say_msg="$(eval_gettext "Submodule path '\$displaypath': '\$command \$sha1'")"
-				must_die_on_failure=yes
-				;;
-			*)
-				die "fatal: $(eval_gettext "Invalid update mode '$update_module' for submodule path '$path'")"
-			esac
-
-			if (sanitize_submodule_env; cd "$sm_path" && $command "$sha1")
-			then
-				say "$say_msg"
-			elif test -n "$must_die_on_failure"
-			then
-				die_with_status 2 "$die_msg"
-			else
-				err="${err};$die_msg"
-				continue
-			fi
-		fi
+		out=$(git submodule--helper run-update-procedure \
+			  ${wt_prefix:+--prefix "$wt_prefix"} \
+			  ${GIT_QUIET:+--quiet} \
+			  ${force:+--force} \
+			  ${just_cloned:+--just-cloned} \
+			  ${nofetch:+--no-fetch} \
+			  ${depth:+"$depth"} \
+			  ${update:+--update "$update"} \
+			  ${prefix:+--recursive-prefix "$prefix"} \
+			  ${sha1:+--oid "$sha1"} \
+			  ${subsha1:+--suboid "$subsha1"} \
+			  "--" \
+			  "$sm_path")
+
+		# exit codes for run-update-procedure:
+		# 0: update was successful, say command output
+		# 1: update procedure failed, but should not die
+		# 2 or 128: subcommand died during execution
+		# 3: no update procedure was run
+		res="$?"
+		case $res in
+		0)
+			say "$out"
+			;;
+		1)
+			err="${err};fatal: $out"
+			continue
+			;;
+		2|128)
+			die_with_status $res "fatal: $out"
+			;;
+		esac
 
 		if test -n "$recursive"
 		then