add apk-repositories(5)

doc/Makefile

@@ -5,6 +5,7 @@ $(obj)/%.8: $(src)/%.8.scd
 	$(SCDOC) < $< > $@
 
 docs: $(obj)/apk.8 \
+	$(obj)/apk-repositories.5 \
 	$(obj)/apk-world.5
 targets += docs
 

doc/apk-repositories.5.scd

@@ -0,0 +1,40 @@
+apk-repositories(5)
+
+# NAME
+
+*/etc/apk/repositories* - list of package repositories
+
+# DESCRIPTION
+
+/etc/apk/repositories is the list of package repositories *apk*(8) uses to
+retrieve package files for installation. Each line of this file specifies the
+location of a package repository, and optionally a tag.
+
+The location may be an _http://_, _https://_, or _ftp://_ URL, or the path to a
+directory on the local filesystem. A tagged repository is prefixed with the
+*@tag* specifier, followed by a space and the repository location. For more
+information about repository tags, see *apk-world*(5).
+
+# REPOSITORY LAYOUT
+
+Each repository must store an index at *$repository/$arch/APKINDEX.tar.gz*. See
+*apk-index*(8) for information about generating this file. The packages
+themselves are stored at *$repository/$arch/$pkgname-$pkgver-r$pkgrel.apk*.
+
+*apk*(8) verifies that each of these files has a valid cryptographic signature
+unless explicitly told not to via the *--allow-untrusted* flag. See
+*abuild-keygen*(1) for information about generating keys, *apk-keys*(5) to add
+keys to the list of trusted keys, *abuild-sign*(1) for information about using
+these keys to sign files, and *apk-verify*(8) for information about verifying
+those signatures.
+
+# UPDATING INDICIES
+
+*apk*(8) fetches and stores the index for each package repository at
+/var/lib/cache. To fetch fresh indicies for all configured repositories, use
+*apk-update*(8).
+
+# AUTHORS
+
+Natanael Copa <ncopa@alpinelinux.org>++
+Timo Teräs <_timo.teras@iki.fi_>