repo_setup: Add check/setup_gitattributes

setup_gitattributes() sets up .git/info/attributes in a way to prevent
transformations from interfering with packaging, because the working tree
files can differ from the Git revision history (and from the source packages).

Similar functionality has been implemented by dgit and git-deborig, so we try
to stay compatible and re-use the name of the attribute macro. Since dgit doesn’t
disable export-subst and export-ignore, which may interfere with export-orig, we
add this on top the same way git-deborig does.

dgit used to have an older preset missing some of the attributes, so if
we find those, we disable them.

The user, should they choose so, still can re-enable the attributes
disabled in this way by adding more specific rules further in the
.git/info/attributes file.

Signed-off-by: Andrej Shadura <andrew.shadura@collabora.co.uk>

1 files changed, 94 insertions, 0 deletions

diff --git a/gbp/scripts/common/repo_setup.py b/gbp/scripts/common/repo_setup.py
index d76b585c..50e9cbf1 100644
--- a/gbp/scripts/common/repo_setup.py
+++ b/gbp/scripts/common/repo_setup.py
@@ -1,6 +1,8 @@
 # vim: set fileencoding=utf-8 :
 #
 # (C) 2006-2011, 2016 Guido Günther <agx@sigxcpu.org>
+# (C) 2021 Andrej Shadura <andrew@shadura.me>
+# (C) 2021 Collabora Limited
 #    This program is free software; you can redistribute it and/or modify
 #    it under the terms of the GNU General Public License as published by
 #    the Free Software Foundation; either version 2 of the License, or
@@ -18,6 +20,10 @@
 """Common repository setup functionality."""
 
 import os
+import re
+import gbp.log
+
+from pathlib import Path
 
 
 def set_user_name_and_email(repo_user, repo_email, repo):
@@ -28,3 +34,91 @@ def set_user_name_and_email(repo_user, repo_email, repo):
     if repo_email == 'DEBIAN':
         if os.getenv('DEBEMAIL'):
             repo.set_user_email(os.getenv('DEBEMAIL'))
+
+
+def check_gitattributes(repo, treeish) -> bool:
+    """
+    Verify the treeish doesn’t contain non-empty .gitattributes files.
+    """
+    for mode, _type, sha1, size, path in repo.list_tree(treeish, recurse=True, sizes=True):
+        if size == 0:
+            continue
+        if path == b'.gitattributes' or path.endswith(b'/.gitattributes'):
+            gbp.log.debug("Found non-empty .gitattributes: %s" % path)
+            return False
+    return True
+
+
+dgit_attr_macro_re = re.compile(r'^\[attr\]dgit-defuse-attrs\s')
+dgit_attr_macro_defn = '-text -eol -crlf -ident -filter -working-tree-encoding'
+attr_glob_defns = {
+    'dgit-defuse-attrs',
+    '-export-subst',
+    '-export-ignore',
+}
+
+
+def is_gitattributes_set_up(repo) -> bool:
+    """
+    Return True if git attributes have been set up correctly:
+        * dgit-defuse-attrs macro exists
+        * dgit-defuse-attrs includes attributes we’re interested in
+        * dgit-defuse-attrs is enabled for *
+        * export-subst and export-ignore are unset for *
+    """
+    gitattrs = Path(repo.git_dir) / 'info' / 'attributes'
+    if not gitattrs.exists():
+        return False
+    dgit_macro_present = False
+    attrs = set()
+    for line in gitattrs.read_text().splitlines():
+        if dgit_attr_macro_re.match(line):
+            gbp.log.debug("Found Git attribute macro: %s" % line)
+            dgit_macro_present = line.endswith(dgit_attr_macro_defn)
+            continue
+        attr = line.split()
+        if attr[0] == '*' and len(attr) == 2:
+            attrs.add(attr[1])
+    gbp.log.debug("Found global Git attributes: %s" % ', '.join(attrs))
+    return dgit_macro_present and attrs >= attr_glob_defns
+
+
+def setup_gitattributes(repo, treeish='HEAD'):
+    """
+    Setup .git/info/attributes in a way to prevent transformations from interfering
+    with packaging, because the working tree files can differ from the Git revision
+    history (and from the source packages).
+
+    Similar functionality has been implemented by dgit and git-deborig, so we try
+    to stay compatible and re-use the name of the attribute macro. Since dgit doesn’t
+    disable export-subst and export-ignore, which may interfere with export-orig, we
+    add this on top the same way git-deborig does.
+    """
+    if is_gitattributes_set_up(repo):
+        return
+    gbp.log.debug("Configuring Git attributes")
+    gitattrs = Path(repo.git_dir) / 'info' / 'attributes'
+    new_attributes = []
+    if not gitattrs.exists():
+        gitattrs.parent.mkdir(exist_ok=True)
+    else:
+        for line in gitattrs.read_text().splitlines():
+            attr = line.split()
+            if attr[0] == '*' and len(attr) == 2:
+                if attr[1] in attr_glob_defns:
+                    continue
+            if dgit_attr_macro_re.match(line):
+                new_attributes += [
+                    "# Old dgit macro disabled:",
+                    "# %s" % line,
+                ]
+                gbp.log.debug("Disabling old dgit macro: '%s'" % line)
+            else:
+                new_attributes.append(line)
+    new_attributes += [
+        "# Added by git-buildpackage to disable .gitattributes found in the upstream tree",
+        "[attr]dgit-defuse-attrs  %s" % dgit_attr_macro_defn,
+    ] + ['* %s' % attr for attr in attr_glob_defns]
+    with gitattrs.with_suffix('.new') as newattrs:
+        newattrs.write_text('\n'.join(new_attributes))
+        newattrs.rename(gitattrs)