add use-<proj>-custom FOO for any commit/branch/tag

While it was possible before to build any branch of mpv/ffmpeg/etc by
just git checkout $whatever and then ./build, it got reset after
./rebuild or ./update etc.

Add use-mpv-custom and use-ffmpeg-custom which accept any
commit/branch/tag which will survive ./rebuild, ./update, etc.

This should make it slightly easier to build past versions of mpv.

While at it, also add use-libass-{master|custom}

6 files changed, 51 insertions, 8 deletions

diff --git a/README.rst b/README.rst
index 8a70fc0..d1aa4e7 100644
--- a/README.rst
+++ b/README.rst
@@ -181,8 +181,13 @@ And run ``./rebuild`` or similar. Use this to switch back to git master:
 
     ./use-mpv-master
 
-Likewise, you can use ``./use-ffmpeg-master`` and ``./use-ffmpeg-release`` to
-switch between git master and the latest FFmpeg release.
+Or this to switch to a custom tag/branch/commit FOO:
+
+    ./use-mpv-custom FOO
+
+Likewise, you can use ``./use-ffmpeg-master``, ``./use-ffmpeg-release`` or
+``./use-ffmpeg-custom BAR`` to switch between git master, the latest FFmpeg
+release, or to a custom tag/branch/commit BAR.
 
 Use on your own risk.
 
diff --git a/update b/update
index d966018..dfe16f8 100755
--- a/update
+++ b/update
@@ -65,21 +65,24 @@ do_fixedref()
     )
 }
 
-# args: $1: project name, $2: release/master [,$3: non-empty to ignore the config file]
+# args: $1: project name, $2: release/master/@foo [,$3: non-empty to ignore the config file]
 checkout()
 {
-    local arg="$2"
+    local branch="$2"
     if [ -z "$3" ] && [ -d config/ ] && [ -f config/branch-$1 ]; then
-        arg="$(cat config/branch-$1)"
+        branch="$(cat config/branch-$1)"
     fi
 
-    case "$arg" in
+    case "$branch" in
         master)  do_gitmaster $1;;
-        *)       do_releasetag $1;;
+        release) do_releasetag $1;;
+        @*)      do_fixedref $1 "${branch#@}";;  # everything after the '@' prefix
+        *)       >&2 printf "%s\n" "Error: Don't know how to checkout '$branch'"
+                 return 1
     esac
 }
 
-# fallback targets: release/master if no config file
+# fallback targets: release/master/@foo if no config file
 checkout_ffmpeg=master
 #checkout_fribidi=release
 checkout_libass=master
diff --git a/use-ffmpeg-custom b/use-ffmpeg-custom
new file mode 100755
index 0000000..025edeb
--- /dev/null
+++ b/use-ffmpeg-custom
@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+export LC_ALL=C
+
+if [ -z "$1" ]; then
+    echo "Aborting. Please provide a commit hash or a tag/branch name."
+    exit 1
+fi
+
+scripts/switch-branch ffmpeg "@$1"
diff --git a/use-libass-custom b/use-libass-custom
new file mode 100755
index 0000000..6bc2475
--- /dev/null
+++ b/use-libass-custom
@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+export LC_ALL=C
+
+if [ -z "$1" ]; then
+    echo "Aborting. Please provide a commit hash or a tag/branch name."
+    exit 1
+fi
+
+scripts/switch-branch libass "@$1"
diff --git a/use-libass-master b/use-libass-master
new file mode 100755
index 0000000..f645acb
--- /dev/null
+++ b/use-libass-master
@@ -0,0 +1,5 @@
+#!/bin/sh
+set -e
+export LC_ALL=C
+
+scripts/switch-branch libass master
diff --git a/use-mpv-custom b/use-mpv-custom
new file mode 100755
index 0000000..cea8d10
--- /dev/null
+++ b/use-mpv-custom
@@ -0,0 +1,10 @@
+#!/bin/sh
+set -e
+export LC_ALL=C
+
+if [ -z "$1" ]; then
+    echo "Aborting. Please provide a commit hash or a tag/branch name."
+    exit 1
+fi
+
+scripts/switch-branch mpv "@$1"