Documentation: refactor "api-index.sh" for out-of-tree builds

The "api-index.sh" script generates an index of API-related
documentation. The script does not handle out-of-tree builds and thus
cannot be used easily by Meson.

Refactor it to be independent of locations by both accepting a source
directory where the API docs live as well as a path to an output file.

Signed-off-by: Patrick Steinhardt <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: pks-t

Documentation/Makefile

@@ -367,7 +367,7 @@ user-manual.xml: user-manual.txt $(ASCIIDOC_DEPS)
 
 technical/api-index.txt: technical/api-index-skel.txt \
 	technical/api-index.sh $(patsubst %,%.txt,$(API_DOCS))
-	$(QUIET_GEN)cd technical && '$(SHELL_PATH_SQ)' ./api-index.sh
+	$(QUIET_GEN)'$(SHELL_PATH_SQ)' technical/api-index.sh ./technical ./technical/api-index.txt
 
 technical/%.html: ASCIIDOC_EXTRA += -a git-relative-html-prefix=../
 $(patsubst %,%.html,$(API_DOCS) technical/api-index $(TECH_DOCS)): %.html : %.txt \

Documentation/technical/api-index.sh

@@ -1,6 +1,17 @@
 #!/bin/sh
 
+if test $# -ne 2
+then
+	echo >&2 "USAGE: $0 <SOURCE_DIR> <OUTPUT>"
+	exit 1
+fi
+
+SOURCE_DIR="$1"
+OUTPUT="$2"
+
 (
+	cd "$SOURCE_DIR"
+
 	c=////////////////////////////////////////////////////////////////
 	skel=api-index-skel.txt
 	sed -e '/^\/\/ table of contents begin/q' "$skel"
@@ -18,11 +29,11 @@
 	done
 	echo "$c"
 	sed -n -e '/^\/\/ table of contents end/,$p' "$skel"
-) >api-index.txt+
+) >"$OUTPUT"+
 
-if test -f api-index.txt && cmp api-index.txt api-index.txt+ >/dev/null
+if test -f "$OUTPUT" && cmp "$OUTPUT" "$OUTPUT"+ >/dev/null
 then
-	rm -f api-index.txt+
+	rm -f "$OUTPUT"+
 else
-	mv api-index.txt+ api-index.txt
+	mv "$OUTPUT"+ "$OUTPUT"
 fi