Replace format-version with min-version

  * "min-version" is specified as a <major>.<minor> point version
    and uses the installed BuildStream version instead of having
    a separate versioning number for the format.

  * The presence of "format-version" is now used to indicate
    that we might be loading a BuildStream 1 project.

  * For now, where parsing the version at startup is concerned, and
    also where `bst init` is concerned, we artificially bump the
    detected BuildStream version to 2.0 if we detect a version < 2.0,
    these exceptions can be removed once 2.0 is tagged and released.

Summary of changes:

  _project.py: Now parse "min-version" and detect "format-version" to
               warn about loading a BuildStream 1 project

  _versions.py: Remove obsolete BST_FORMAT_VERSION numbers from here

  data/projectconfig.yaml: Remove old "format-version" from defaults

  utils.py: Added new private _parse_version() helper function, and another
            _get_bst_api_version() to get an adjusted API version.

  frontend/app.py, frontend/cli.py: Updated `bst init` implementation

  testing (buildstream.testing): Updated testing utilities to generate
  and use projects with min-version instead of format-version.

  tests and examples: Updated to use min-version across the board.

15 files changed, 28 insertions, 26 deletions

diff --git a/doc/examples/autotools/project.conf b/doc/examples/autotools/project.conf
index 6c1142340..49c22e925 100644
--- a/doc/examples/autotools/project.conf
+++ b/doc/examples/autotools/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: autotools
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/composition/project.conf b/doc/examples/composition/project.conf
index dc82df72b..7f5fbdac6 100644
--- a/doc/examples/composition/project.conf
+++ b/doc/examples/composition/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: composition
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/developing/project.conf b/doc/examples/developing/project.conf
index 3b0920991..0182d1d5c 100644
--- a/doc/examples/developing/project.conf
+++ b/doc/examples/developing/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: developing 
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/directives/project.conf b/doc/examples/directives/project.conf
index c078a5af8..8cf4c42b5 100644
--- a/doc/examples/directives/project.conf
+++ b/doc/examples/directives/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: directives
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/filtering/project.conf b/doc/examples/filtering/project.conf
index 9a01a7515..cf7db0d87 100644
--- a/doc/examples/filtering/project.conf
+++ b/doc/examples/filtering/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: filtering
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/first-project/project.conf b/doc/examples/first-project/project.conf
index f66376146..d62fc6c12 100644
--- a/doc/examples/first-project/project.conf
+++ b/doc/examples/first-project/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: first-project
 
-# Required BuildStream format version
-format-version: 25
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/flatpak-autotools/project.conf b/doc/examples/flatpak-autotools/project.conf
index 1318014f9..08dc6ee32 100644
--- a/doc/examples/flatpak-autotools/project.conf
+++ b/doc/examples/flatpak-autotools/project.conf
@@ -1,5 +1,7 @@
 name: flatpak-autotools
 
+min-version: 2.0
+
 aliases:
   flathub: https://dl.flathub.org/
 
diff --git a/doc/examples/integration-commands/project.conf b/doc/examples/integration-commands/project.conf
index c6c59906b..63d50264c 100644
--- a/doc/examples/integration-commands/project.conf
+++ b/doc/examples/integration-commands/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: integration-commands
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/junction-includes/project.conf b/doc/examples/junction-includes/project.conf
index e591b78b1..9d1e6f1e9 100644
--- a/doc/examples/junction-includes/project.conf
+++ b/doc/examples/junction-includes/project.conf
@@ -1,5 +1,5 @@
 name: subproject
-format-version: 18
+min-version: 2.0
 element-path: elements
 
 aliases:
diff --git a/doc/examples/junction-includes/subproject/project.conf b/doc/examples/junction-includes/subproject/project.conf
index d9387f244..827e0fb4d 100644
--- a/doc/examples/junction-includes/subproject/project.conf
+++ b/doc/examples/junction-includes/subproject/project.conf
@@ -1,5 +1,5 @@
 name: subproject
-format-version: 18
+min-version: 2.0
 element-path: elements
 
 aliases:
diff --git a/doc/examples/junctions/autotools/project.conf b/doc/examples/junctions/autotools/project.conf
index 216816335..8c0d0a337 100644
--- a/doc/examples/junctions/autotools/project.conf
+++ b/doc/examples/junctions/autotools/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: autotools
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/junctions/project.conf b/doc/examples/junctions/project.conf
index cb9a83716..1a9973004 100644
--- a/doc/examples/junctions/project.conf
+++ b/doc/examples/junctions/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: junctions
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/overlaps/project.conf b/doc/examples/overlaps/project.conf
index 297077220..c54f79cde 100644
--- a/doc/examples/overlaps/project.conf
+++ b/doc/examples/overlaps/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: overlaps
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/running-commands/project.conf b/doc/examples/running-commands/project.conf
index aafb6a9f2..eb9f4012b 100644
--- a/doc/examples/running-commands/project.conf
+++ b/doc/examples/running-commands/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: running-commands
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements
diff --git a/doc/examples/strict-mode/project.conf b/doc/examples/strict-mode/project.conf
index ac73434c8..bd6836b44 100644
--- a/doc/examples/strict-mode/project.conf
+++ b/doc/examples/strict-mode/project.conf
@@ -1,8 +1,8 @@
 # Unique project name
 name: strict-mode
 
-# Required BuildStream format version
-format-version: 18
+# Minimum required BuildStream version
+min-version: 2.0
 
 # Subdirectory where elements are stored
 element-path: elements