Use tab-size from EditorConfig

For projects that use tab width != 8, we need to set the "tab-size"
config option.  Many projects these days 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 wait 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

.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

@@ -18,10 +18,12 @@
 
 bool pager_get_column_data(struct view *view, const struct line *line, struct view_column_data *column_data);
 bool pager_read(struct view *view, struct buffer *buf, bool force_stop);
-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

src/diff.c

@@ -263,7 +263,7 @@ diff_common_read_diff_wdiff_group(struct diff_stat_context *context)
 	return true;
 }
 
-static bool
+static struct line *
 diff_common_read_diff_wdiff(struct view *view, const char *text)
 {
 	struct diff_stat_context context = { text, LINE_DEFAULT };
@@ -282,7 +282,7 @@ diff_common_read_diff_wdiff(struct view *view, const char *text)
 	return diff_common_add_line(view, text, LINE_DEFAULT, &context);
 }
 
-static bool
+static struct line *
 diff_common_highlight(struct view *view, const char *text, enum line_type type)
 {
 	struct diff_stat_context context = { text, type, true };
@@ -303,6 +303,7 @@ bool
 diff_common_read(struct view *view, const char *data, struct diff_state *state)
 {
 	enum line_type type = get_line_type(data);
+	struct line *line;
 
 	/* ADD2 and DEL2 are only valid in combined diff hunks */
 	if (!state->combined_diff && (type == LINE_DIFF_ADD2 || type == LINE_DIFF_DEL2))
@@ -334,7 +335,7 @@ diff_common_read(struct view *view, const char *data, struct diff_state *state)
 	}
 
 	if (!state->after_commit_title && !prefixcmp(data, "    ")) {
-		struct line *line = add_line_text(view, data, LINE_DEFAULT);
+		line = add_line_text(view, data, LINE_DEFAULT);
 
 		if (line)
 			line->commit_title = 1;
@@ -345,13 +346,11 @@ diff_common_read(struct view *view, const char *data, struct diff_state *state)
 	if (type == LINE_DIFF_HEADER) {
 		state->after_diff = true;
 		state->reading_diff_chunk = false;
-
 	} else if (type == LINE_DIFF_CHUNK) {
 		const int len = chunk_header_marker_length(data);
 		const char *context = strstr(data + len, "@@");
-		struct line *line =
-			context ? add_line_text_at(view, view->lines, data, LINE_DIFF_CHUNK, len)
-				: NULL;
+		line = context ? add_line_text_at(view, view->lines, data, LINE_DIFF_CHUNK, len)
+			       : NULL;
 		struct box *box;
 
 		if (!line)
@@ -363,21 +362,34 @@ diff_common_read(struct view *view, const char *data, struct diff_state *state)
 		box->cell[box->cells++].type = LINE_DIFF_STAT;
 		state->combined_diff = (len > 2);
 		state->reading_diff_chunk = true;
-		return true;
+		goto set_tab_width;
 
 	} else if (type == LINE_COMMIT) {
 		state->reading_diff_chunk = false;
 
 	} else if (state->highlight && strchr(data, 0x1b)) {
-		return diff_common_highlight(view, data, type);
-
+		if (!(line = diff_common_highlight(view, data, type)))
+			return false;
+		goto set_tab_width;
 	} else if (opt_word_diff && state->reading_diff_chunk &&
 		   /* combined diff format is not using word diff */
 		   !state->combined_diff) {
-		return diff_common_read_diff_wdiff(view, data);
+		if (!(line = diff_common_read_diff_wdiff(view, data)))
+			return false;
+		goto set_tab_width;
 	}
 
-	return pager_common_read(view, data, type, NULL);
+	return pager_common_read(view, data, type, true, &line);
+
+set_tab_width:
+#if defined HAVE_EDITORCONFIG
+	if (type == LINE_DIFF_CHUNK || type == LINE_DEFAULT ||
+	    type == LINE_DIFF_ADD || type == LINE_DIFF_ADD2 ||
+	    type == LINE_DIFF_DEL || type == LINE_DIFF_DEL2) {
+		line->tab_size = state->common.tab_size;
+	}
+#endif
+	return true;
 }
 
 static bool

src/draw.c

@@ -471,6 +471,12 @@ view_column_draw(struct view *view, struct line *line, unsigned int lineno)
 {
 	struct view_column *column = view->columns;
 	struct view_column_data column_data = {0};
+	int tab_size;
+#if defined HAVE_EDITORCONFIG
+	tab_size = line->tab_size ? line->tab_size : opt_tab_size;
+#else
+	tab_size = opt_tab_size;
+#endif
 
 	if (!view->ops->get_column_data(view, line, &column_data))
 		return true;
@@ -582,13 +588,13 @@ view_column_draw(struct view *view, struct line *line, unsigned int lineno)
 						indent = 0;
 					}
 
-					if (draw_textn(view, cell->type, text, length, opt_tab_size))
+					if (draw_textn(view, cell->type, text, length, tab_size))
 						return true;
 
 					text += length;
 				}
 
-			} else if (draw_text(view, type, text, opt_tab_size)) {
+			} else if (draw_text(view, type, text, tab_size)) {
 				return true;
 			}
 		}

src/log.c

@@ -19,6 +19,9 @@
 #include "tig/pager.h"
 
 struct log_state {
+#if defined HAVE_EDITORCONFIG
+	struct diff_common_state common;
+#endif
 	/* Used for tracking when we need to recalculate the previous
 	 * commit, for example when the user scrolls up or uses the page
 	 * up/down in the log view. */
@@ -142,7 +145,7 @@ log_read(struct view *view, struct buffer *buf, bool force_stop)
 		state->reading_diff_stat = false;
 	}
 
-	if (!pager_common_read(view, data, type, &line))
+	if (!pager_common_read(view, data, type, true, &line))
 		return false;
 	if (line && state->graph_indent)
 		line->graph_indent = 1;