[Buildroot] [PATCH 9/9 v4] docs/manual: add appendix to convert old br2-external trees

[Yann E. MORIN]

Signed-off-by: "Yann E. MORIN" <yann.morin.1998 at free.fr>
Cc: Thomas Petazzoni <thomas.petazzoni at free-electrons.com>
Cc: Arnout Vandecappelle <arnout at mind.be>
Cc: Samuel Martin <s.martin49 at gmail.com>
Cc: Romain Naour <romain.naour at openwide.fr>
Cc: Julien CORJON <corjon.j at ecagroup.com>
---
 docs/manual/appendix.txt                |  2 +-
 docs/manual/br2-external-converting.txt | 39 +++++++++++++++++++++++++++++++++
 docs/manual/customize-outside-br.txt    |  5 +++++
 support/scripts/br2-external            |  7 +++++-
 4 files changed, 51 insertions(+), 2 deletions(-)
 create mode 100644 docs/manual/br2-external-converting.txt

diff --git a/docs/manual/appendix.txt b/docs/manual/appendix.txt
index 87a20bd..cd97744 100644
--- a/docs/manual/appendix.txt
+++ b/docs/manual/appendix.txt
@@ -3,7 +3,7 @@
 
 include::makedev-syntax.txt[]
 include::makeusers-syntax.txt[]
-
+include::br2-external-converting.txt[]
 
 // Automatically generated lists:
 
diff --git a/docs/manual/br2-external-converting.txt b/docs/manual/br2-external-converting.txt
new file mode 100644
index 0000000..444c73d
--- /dev/null
+++ b/docs/manual/br2-external-converting.txt
@@ -0,0 +1,39 @@
+// -*- mode:doc; -*-
+// vim: set syntax=asciidoc:
+
+[[br2-external-converting]]
+== Converting old br2-external trees
+
+Before Buildroot 2016.11, it was possible to use only one br2-external
+tree at once. With Buildroot 2016.11 came the possibility to use more
+than one (for details, see xref:outside-br-custom[]).
+
+This however means that older br2-external trees are not useable as-is.
+A minor change has to be made: adding a name to your br2-external tree.
+
+This can be done very easily in just a few steps:
+
+ * First, create a new file named +external.desc+, at the root of your
+   br2-external tree, with a single line defining the name of your
+   br2-external tree:
++
+----
+$ echo 'name: NAME_OF_YOUR_TREE' >external.desc
+----
++
+.Note
+Be careful when choosing a name: it has to be relatively unique, be made
+with only ASCII characters from the set +[A-Za-z0-9_]+.
+
+ * Then, change every occurence of +BR2_EXTERNAL+ in your br2-external
+   tree with the new value:
++
+----
+$ find . -type f | xargs sed -i 's/BR2_EXTERNAL/BR2_EXTERNAL_NAME_OF_YOUR_TREE_PATH/g'
+----
+
+Now, your br2-external tree can be used with Buildroot 2016.11 onward.
+
+.Note:
+This is change makes your br2-external tree incompatible with Buildroot
+before 2016.11.
diff --git a/docs/manual/customize-outside-br.txt b/docs/manual/customize-outside-br.txt
index b0c7271..c4f6023 100644
--- a/docs/manual/customize-outside-br.txt
+++ b/docs/manual/customize-outside-br.txt
@@ -33,6 +33,11 @@ If it is passed as a relative path, it is important to note that it is
 interpreted relative to the main Buildroot source directory, *not* to
 the Buildroot output directory.
 
+.Note:
+If using an br2-external tree from before Buildroot 2016.11, you need to
+convert it before you can use it with Buildroot 2016.11 onward. See
+xref:br2-external-converting[] for help on doing so.
+
 Some examples:
 
 -----
diff --git a/support/scripts/br2-external b/support/scripts/br2-external
index 9936650..612ae58 100755
--- a/support/scripts/br2-external
+++ b/support/scripts/br2-external
@@ -5,6 +5,10 @@ set -e
 declare -a BR2_EXT_NAMES
 declare -A BR2_EXT_PATHS
 
+# URL to manual for help in converting old br2-external trees.
+# Escape '#' so that make does not consider it a comment.
+MANUAL_URL='https://buildroot.org/manual/manual.html\#br2-external-converting'
+
 main() {
     local OPT OPTARG
     local br2_ext ofile ofmt
@@ -77,7 +81,8 @@ do_validate_one() {
         error "'%s': no such file or directory\n" "${br2_ext}"
     fi
     if [ ! -f "${br2_ext}/external.desc" ]; then
-        error "'%s': does not have a name (in 'external.desc')\n" "${br2_ext}"
+        error "'%s': does not have a name (in 'external.desc'). See %s\n" \
+            "${br2_ext}" "${MANUAL_URL}"
     fi
     br2_name="$(sed -r -e '/^name: +(.*)$/!d; s//\1/' "${br2_ext}/external.desc")"
     if [ -z "${br2_name}" ]; then
-- 
2.7.4