[gimp] Add script to install files in the dist tarball. Add a check inside Meson to detect if we're buildin

[Jehan <jehanp src gnome org>]

commit 9cd0584e9029ca14b9f52e62571b3b1f34963da7
Author: Félix Piédallu <felix piedallu me>
Date:   Fri Nov 8 13:17:08 2019 +0100

    Add script to install files in the dist tarball.
    Add a check inside Meson to detect if we're building from a git clone
    or a dist tarball.
    (in thie later, don't generated INSTALL.in and git-version.h)

 meson.build          | 77 ++++++++++++++++++++++++++++++----------------------
 meson_dist_script.sh |  6 ++++
 2 files changed, 50 insertions(+), 33 deletions(-)
---
diff --git a/meson.build b/meson.build
index 23f95889a1..2930751ce3 100644
--- a/meson.build
+++ b/meson.build
@@ -15,6 +15,11 @@ conf = configuration_data()
 
 warnings = []
 
+# git-version.h is already present and not generated if dist tarball
+is_dist_tarball = run_command('python', '-c',
+  'import sys,os; sys.exit(0 if os.path.exists("git-version.h") else 1)'
+).returncode() == 0
+
 ################################################################################
 # Project info
 
@@ -919,20 +924,20 @@ else
 
   if (not python_found) and (not always_install)
     error('''
-    Python @0@ or PyGObject was not found.
+    Python >=@0@ or PyGObject was not found.
     Note that you may install the Python plug-ins even if you have no Python
     interpreter at build-time by passing the configure option -Dpython=always.
-    Just make sure that a Python @0@ interpreter is available at run-time.
-    '''.format(python3_required_version))
+    Just make sure that a Python >=@0@ interpreter is available at run-time.
+    '''.format(python3_minver))
   endif
 
   if (not python_found) and (always_install)
     python_warning = '''
-    Python @0@ or PyGObject was not found.
+    Python >=@0@ or PyGObject was not found.
     Python plug-ins will be installed anyway but you should make sure that
     a compatible Python interpreter is available at installation, otherwise
     installed plug-ins won't be usable.
-    '''.format(python3_required_version)
+    '''.format(python3_minver)
     warning(python_warning)
     warnings += python_warning
   endif
@@ -1401,29 +1406,31 @@ endif
   #####   ####  #    # #      #  ####     #       # ###### ######  ####
 
 
-
-gitversion_h1 = vcs_tag(
-  input : 'app/git-version.h.in',
-  output: 'git-version.h.in.1',
-  command: [ 'git', 'describe', '--always', ],
-  replace_string: '@GIMP_GIT_VERSION@',
-  fallback: '',
-)
-gitversion_h2 = vcs_tag(
-  input : gitversion_h1,
-  output: 'git-version.h.in.2',
-  command: [ 'git', 'rev-parse', '--short', 'HEAD', ],
-  replace_string: '@GIMP_GIT_VERSION_ABBREV@',
-  fallback: '',
-)
-gitversion_h = vcs_tag(
-  input : gitversion_h2,
-  output: 'git-version.h',
-  command: [ 'git', 'log', '-n1', '--date=format:%Y', '--pretty=%cd', ],
-  replace_string: '@GIMP_GIT_LAST_COMMIT_YEAR@',
-  fallback: '',
-)
-
+if is_dist_tarball
+  gitversion_h = files('git-version.h')
+else
+  gitversion_h1 = vcs_tag(
+    input : 'app/git-version.h.in',
+    output: 'git-version.h.in.1',
+    command: [ 'git', 'describe', '--always', ],
+    replace_string: '@GIMP_GIT_VERSION@',
+    fallback: '',
+  )
+  gitversion_h2 = vcs_tag(
+    input : gitversion_h1,
+    output: 'git-version.h.in.2',
+    command: [ 'git', 'rev-parse', '--short', 'HEAD', ],
+    replace_string: '@GIMP_GIT_VERSION_ABBREV@',
+    fallback: '',
+  )
+  gitversion_h = vcs_tag(
+    input : gitversion_h2,
+    output: 'git-version.h',
+    command: [ 'git', 'log', '-n1', '--date=format:%Y', '--pretty=%cd', ],
+    replace_string: '@GIMP_GIT_LAST_COMMIT_YEAR@',
+    fallback: '',
+  )
+endif
 
 install_conf = configuration_data()
 install_conf.set('GIMP_APP_VERSION', gimp_app_version)
@@ -1460,11 +1467,13 @@ install_conf.set('WEBP_REQUIRED_VERSION',         webp_minver)
 install_conf.set('WMF_REQUIRED_VERSION',          wmf_minver)
 install_conf.set('XGETTEXT_REQUIRED_VERSION',     '0.19')
 
-configure_file(
-  input : 'INSTALL.in',
-  output: 'INSTALL',
-  configuration: install_conf
-)
+if not is_dist_tarball
+  INSTALL = configure_file(
+    input : 'INSTALL.in',
+    output: 'INSTALL',
+    configuration: install_conf
+  )
+endif
 
 
 configure_file(
@@ -1547,6 +1556,8 @@ custom_target('Changelog',
   build_by_default: false,
 )
 
+meson.add_dist_script('meson_dist_script.sh')
+
 
 ################################################################################
 # Subdirs
diff --git a/meson_dist_script.sh b/meson_dist_script.sh
new file mode 100755
index 0000000000..e61da177a7
--- /dev/null
+++ b/meson_dist_script.sh
@@ -0,0 +1,6 @@
+#!/usr/bin/env bash
+
+cp -f 'INSTALL' "${MESON_DIST_ROOT}"
+# rm -f "${MESON_DIST_ROOT}/INSTALL.in"
+
+cp 'git-version.h' "${MESON_DIST_ROOT}"