filter-repo: add option --report-dir to set custom analysis dir

--analyze is hardcoded to write to a subdirectory inside GIT_DIR.

When practicing filtering runs on a large repo it is desirable to keep
an unchanged copy read-only to reduce chance of user error. It is
desirable to be able to analyze a read-only repo without having to clone
it. This would save a lot of time and space.

Add --report-dir option to set a non-default destination directory for
writing analysis output to.

Signed-off-by: rndbit <rndbit@filter.bitman.net>
[en: fixed existing regression test broken by now not overwriting the
     analysis directory unconditionally, and also added a new test of
     the new behavior for code coverage.]
Signed-off-by: Elijah Newren <newren@gmail.com>

git-filter-repo

@@ -1758,6 +1758,12 @@ EXAMPLES
         help=_("Analyze repository history and create a report that may be "
                "useful in determining what to filter in a subsequent run. "
                "Will not modify your repo."))
+    analyze.add_argument('--report-dir',
+        metavar='DIR_OR_FILE',
+        type=os.fsencode,
+        dest='report_dir',
+        help=_("Directory to write report, defaults to GIT_DIR/filter_repo/analysis,"
+               "refuses to run if exists, --force delete existing dir first."))
 
     path = parser.add_argument_group(title=_("Filtering based on paths "
                                              "(see also --filename-callback)"))
@@ -2641,15 +2647,25 @@ class RepoAnalyze(object):
 
   @staticmethod
   def run(args):
-    git_dir = GitUtils.determine_git_dir(b'.')
+    if args.report_dir:
+      reportdir = args.report_dir
+    else:
+      git_dir = GitUtils.determine_git_dir(b'.')
 
     # Create the report directory as necessary
-    results_tmp_dir = os.path.join(git_dir, b'filter-repo')
-    if not os.path.isdir(results_tmp_dir):
-      os.mkdir(results_tmp_dir)
-    reportdir = os.path.join(results_tmp_dir, b"analysis")
-    if not args.force and os.path.isdir(reportdir):
-      shutil.rmtree(reportdir)
+      results_tmp_dir = os.path.join(git_dir, b'filter-repo')
+      if not os.path.isdir(results_tmp_dir):
+        os.mkdir(results_tmp_dir)
+      reportdir = os.path.join(results_tmp_dir, b"analysis")
+
+    if os.path.isdir(reportdir):
+      if args.force:
+        sys.stdout.write(_("Warning: Removing recursively: \"%s\"") % decode(reportdir))
+        shutil.rmtree(reportdir)
+      else:
+        sys.stdout.write(_("Error: dir already exists (use --force to delete): \"%s\"\n") % decode(reportdir))
+        sys.exit(1)
+
     os.mkdir(reportdir)
 
     # Gather the data we need

t/t9390-filter-repo.sh

@@ -722,8 +722,11 @@ test_expect_success C_LOCALE_OUTPUT '--analyze' '
 
 		git filter-repo --analyze &&
 
-		# It should work and overwrite report if run again
-		git filter-repo --analyze &&
+		# It should not work again without a --force
+		test_must_fail git filter-repo --analyze &&
+
+		# With a --force, another run should succeed
+		git filter-repo --analyze --force &&
 
 		test -d .git/filter-repo/analysis &&
 		cd .git/filter-repo/analysis &&
@@ -824,6 +827,38 @@ test_expect_success C_LOCALE_OUTPUT '--analyze' '
 	)
 '
 
+test_expect_success C_LOCALE_OUTPUT '--analyze --report-dir' '
+	setup_analyze_me &&
+	(
+		cd analyze_me &&
+
+		rm -rf .git/filter-repo &&
+		git filter-repo --analyze --report-dir foobar &&
+
+		# It should not work again without a --force
+		test_must_fail git filter-repo --analyze --report-dir foobar &&
+
+		# With a --force, though, it should overwrite
+		git filter-repo --analyze --report-dir foobar --force &&
+
+		test ! -d .git/filter-repo/analysis &&
+		test -d foobar &&
+
+		cd foobar &&
+
+		# Very simple tests because already tested above.
+		test_path_is_file renames.txt &&
+		test_path_is_file README &&
+		test_path_is_file blob-shas-and-paths.txt &&
+		test_path_is_file directories-all-sizes.txt &&
+		test_path_is_file directories-deleted-sizes.txt &&
+		test_path_is_file extensions-all-sizes.txt &&
+		test_path_is_file extensions-deleted-sizes.txt &&
+		test_path_is_file path-all-sizes.txt &&
+		test_path_is_file path-deleted-sizes.txt
+	)
+'
+
 test_expect_success '--replace-text all options' '
 	setup_analyze_me &&
 	(