Use tab-size from EditorConfig

For projects that use tab width != 8, users want to set the "tab-size"
config option.  Many projects these days already state their preference
in a ".editorconfig" file. GitHub honors that file when rendering
diffs and blobs.

Add an optional dependency to the EditorConfig library to read such
files. Prefer the tab-size from EditorConfig, over the "tab-size"
config option. Not being able to override the EditorConfig tab-size
seems counterintuitive but I don't see why someone would want that,
so I'd mayb ewait until someone complains. If we want that we could
implement a "tab-size-from-editorconfig" option that defaults to true.

Implementation hiccups:

Unfortunately, we currently don't always fill "repo.worktree" - only
in the special cases where either of $GIT_WORK_TREE or core.worktree is
defined. Hence we need to run an extra "git rev-parse --show-toplevel".
We do run "git rev-parse --is-inside-worktree [...]" elsewhere but
we can't add "--show-toplevel" to that call or else we'd fail when
run in bare repos.

The use of diff_get_pathname() is a bit wasteful, we should probably
refactor this to just remember the last line of type LINE_DIFF_ADD_FILE
or LINE_DIFF_HEADER.

Closes #840

Author: krobelus

.github/workflows/linux.yml

@@ -28,5 +28,8 @@ jobs:
           export LANG=en_US.utf8
           sudo apt update
           sudo DEBIAN_FRONTEND=noninteractive apt -yq install --no-install-recommends \
-            asciidoc valgrind xmlto
+            asciidoc \
+            libeditorconfig-dev \
+            valgrind \
+            xmlto
           CC=${{ matrix.compiler }} TIG_BUILD=${{ matrix.tig_build }} tools/travis.sh

.github/workflows/macos.yml

@@ -45,5 +45,13 @@ jobs:
       - name: Test Tig
         shell: 'script -q typescript sh {0}' # Workaround to get a TTY, see https://github.com/gfx/example-github-actions-with-tty
         run: |
-          brew install asciidoc autoconf automake coreutils gnu-sed ncurses xmlto
+          brew install \
+            asciidoc \
+            autoconf \
+            automake \
+            coreutils \
+            editorconfig \
+            gnu-sed \
+            ncurses \
+            xmlto
           TIG_BUILD=autoconf tools/travis.sh

INSTALL.adoc

@@ -206,6 +206,8 @@ configure script and building documentation:
 				 search and command prompts.
 |PCRE				|Adds support for Perl Compatible Regular
 				 Expressions in searches.
+|EditorConfig core library      |Adds support for setting tab-size based on
+                                 an .editorconfig file.
 |autoconf			|Contains autoreconf for generating configure
 				 from configure.ac.
 |asciidoc (>= 8.4)		|Generates HTML and (DocBook) XML from text.

NEWS.adoc

@@ -1,6 +1,13 @@
 Release notes
 =============
 
+master
+------
+
+Improvements:
+
+- Honor tab width from EditorConfig by linking against the EditorConfig core library. (#1239)
+
 tig-2.5.7
 ---------
 

configure.ac

@@ -58,6 +58,16 @@ AS_IF([test "x$with_pcre" != xno], [
 	])
 ])
 
+dnl Check for EditorConfig library
+AC_ARG_WITH(editorconfig, [AS_HELP_STRING([--without-editorconfig], [do not use the EditorConfig library])])
+AS_IF([test "x$with_editorconfig" != xno], [
+	AC_CHECK_HEADERS([editorconfig/editorconfig.h])
+	AS_IF([test "x$ac_cv_header_editorconfig_editorconfig_h" = xyes], [
+		AC_DEFINE([HAVE_EDITORCONFIG], [1], [Define if you have EditorConfig])
+		LIBS="$LIBS -leditorconfig"
+	])
+])
+
 dnl OS-specific
 case $(uname -s 2>/dev/null || echo unknown) in "OS400")
 	AC_CHECK_LIB(util, main, [LIBS="$LIBS -lutil"], AC_MSG_ERROR([Please install the libutil-devel package]))

doc/tigrc.5.adoc

@@ -269,6 +269,7 @@ The following variables can be set:
 'tab-size' (int)::
 
 	Number of spaces per tab. The default is 8 spaces.
+        This may be overridden by an EditorConfig file.
 
 'diff-context' (int)::
 

include/tig/diff.h

@@ -16,7 +16,16 @@
 
 #include "tig/view.h"
 
+#if defined HAVE_EDITORCONFIG
+struct diff_common_state {
+		uint8_t tab_size;
+};
+#endif
+
 struct diff_state {
+#if defined HAVE_EDITORCONFIG
+	struct diff_common_state common;
+#endif
 	bool after_commit_title;
 	bool after_diff;
 	bool reading_diff_chunk;

include/tig/pager.h

@@ -17,10 +17,12 @@
 #include "tig/view.h"
 
 bool pager_get_column_data(struct view *view, const struct line *line, struct view_column_data *column_data);
-bool pager_common_read(struct view *view, const char *data, enum line_type type, struct line **line);
+bool pager_common_read(struct view *view, const char *data, enum line_type type, bool is_diff, struct line **line);
 enum request pager_request(struct view *view, enum request request, struct line *line);
 void pager_select(struct view *view, struct line *line);
 
+uint8_t editorconfig_tab_size(const char file[]);
+
 extern struct view pager_view;
 
 static inline void

include/tig/view.h

@@ -39,6 +39,9 @@ struct box {
 struct line {
 	enum line_type type;
 	unsigned int lineno:24;
+#if defined HAVE_EDITORCONFIG
+	unsigned int tab_size:8;
+#endif
 
 	/* State flags */
 	unsigned int selected:1;

src/blob.c

@@ -14,6 +14,7 @@
 #include "tig/refdb.h"
 #include "tig/parse.h"
 #include "tig/repo.h"
+#include "tig/diff.h"
 #include "tig/display.h"
 #include "tig/draw.h"
 #include "tig/ui.h"
@@ -22,6 +23,9 @@
 #include "tig/blob.h"
 
 struct blob_state {
+#if defined HAVE_EDITORCONFIG
+	struct diff_common_state common;
+#endif
 	char commit[SIZEOF_REF];
 	const char *file;
 };
@@ -90,6 +94,10 @@ blob_open(struct view *view, enum open_flags flags)
 	else
 		string_copy_rev(view->ref, view->ops->id);
 
+#if defined HAVE_EDITORCONFIG
+	state->common.tab_size = editorconfig_tab_size(view->env->file);
+#endif
+
 	return begin_update(view, NULL, argv, flags);
 }
 
@@ -104,7 +112,7 @@ blob_read(struct view *view, struct buffer *buf, bool force_stop)
 		return true;
 	}
 
-	return pager_common_read(view, buf->data, LINE_DEFAULT, NULL);
+	return pager_common_read(view, buf->data, LINE_DEFAULT, false, NULL);
 }
 
 static void