diff: vary default prefix depending on what are compared

With a new configuration "diff.mnemonicprefix", "git diff" shows the
differences between various combinations of preimage and postimage trees
with prefixes different from the standard "a/" and "b/".  Hopefully this
will make the distinction stand out for some people.

    "git diff" compares the (i)ndex and the (w)ork tree;
    "git diff HEAD" compares a (c)ommit and the (w)ork tree;
    "git diff --cached" compares a (c)ommit and the (i)ndex;
    "git-diff HEAD:file1 file2" compares an (o)bject and a (w)ork tree entity;
    "git diff --no-index a b" compares two non-git things (1) and (2).

Because these mnemonics now have meanings, they are swapped when reverse
diff is in effect and this feature is enabled.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 81f981509a2b9c129b31772dee5b859b3f1a2315..74af36de5cadf36041fcf9f33ca52837c452689f 100644 (file)
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -581,6 +581,22 @@ diff.external::
        you want to use an external diff program only on a subset of
        your files, you might want to use linkgit:gitattributes[5] instead.
 
+diff.mnemonicprefix::
+       If set, 'git-diff' uses a prefix pair that is different from the
+       standard "a/" and "b/" depending on what is being compared.  When
+       this configuration is in effect, reverse diff output also swaps
+       the order of the prefixes:
+'git-diff';;
+       compares the (i)ndex and the (w)ork tree;
+'git-diff HEAD';;
+        compares a (c)ommit and the (w)ork tree;
+'git diff --cached';;
+       compares a (c)ommit and the (i)ndex;
+'git-diff HEAD:file1 file2';;
+       compares an (o)bject and a (w)ork tree entity;
+'git diff --no-index a b';;
+       compares two non-git things (1) and (2).
+
 diff.renameLimit::
        The number of files to consider when performing the copy/rename
        detection; equivalent to the 'git-diff' option '-l'.

diff --git a/builtin-diff.c b/builtin-diff.c
index 7ffea975059f9e13b07ca680e6707ffc14973f90..266337b832a020b97ab59cefb4ea1f05404fd00b 100644 (file)
--- a/builtin-diff.c
+++ b/builtin-diff.c
@@ -74,6 +74,8 @@ static int builtin_diff_b_f(struct rev_info *revs,
        if (!(S_ISREG(st.st_mode) || S_ISLNK(st.st_mode)))
                die("'%s': not a regular file or symlink", path);
 
+       diff_set_mnemonic_prefix(&revs->diffopt, "o/", "w/");
+
        if (blob[0].mode == S_IFINVALID)
                blob[0].mode = canon_mode(st.st_mode);
 

diff --git a/combine-diff.c b/combine-diff.c
index 4dfc33086755e7ae03310baabd0060149f323f4c..19bd60e34626d07cf7f3df96a20a88503692d692 100644 (file)
--- a/combine-diff.c
+++ b/combine-diff.c
@@ -675,9 +675,13 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
        int i, show_hunks;
        int working_tree_file = is_null_sha1(elem->sha1);
        int abbrev = DIFF_OPT_TST(opt, FULL_INDEX) ? 40 : DEFAULT_ABBREV;
+       const char *a_prefix, *b_prefix;
        mmfile_t result_file;
 
        context = opt->context;
+       a_prefix = opt->a_prefix ? opt->a_prefix : "a/";
+       b_prefix = opt->b_prefix ? opt->b_prefix : "b/";
+
        /* Read the result of merge first */
        if (!working_tree_file)
                result = grab_blob(elem->sha1, &result_size);
@@ -853,13 +857,13 @@ static void show_patch_diff(struct combine_diff_path *elem, int num_parent,
                        dump_quoted_path("--- ", "", "/dev/null",
                                         c_meta, c_reset);
                else
-                       dump_quoted_path("--- ", opt->a_prefix, elem->path,
+                       dump_quoted_path("--- ", a_prefix, elem->path,
                                         c_meta, c_reset);
                if (deleted)
                        dump_quoted_path("+++ ", "", "/dev/null",
                                         c_meta, c_reset);
                else
-                       dump_quoted_path("+++ ", opt->b_prefix, elem->path,
+                       dump_quoted_path("+++ ", b_prefix, elem->path,
                                         c_meta, c_reset);
                dump_sline(sline, cnt, num_parent,
                           DIFF_OPT_TST(opt, COLOR_DIFF));

diff --git a/diff-lib.c b/diff-lib.c
index e7eaff9a68ccbcc692522c9956f0dae9af45f3f1..ae96c64ca209f4df9008198e8a04b160bed618c7 100644 (file)
--- a/diff-lib.c
+++ b/diff-lib.c
@@ -63,6 +63,8 @@ int run_diff_files(struct rev_info *revs, unsigned int option)
                              ? CE_MATCH_RACY_IS_DIRTY : 0);
        char symcache[PATH_MAX];
 
+       diff_set_mnemonic_prefix(&revs->diffopt, "i/", "w/");
+
        if (diff_unmerged_stage < 0)
                diff_unmerged_stage = 2;
        entries = active_nr;
@@ -469,6 +471,7 @@ int run_diff_index(struct rev_info *revs, int cached)
        if (unpack_trees(1, &t, &opts))
                exit(128);
 
+       diff_set_mnemonic_prefix(&revs->diffopt, "c/", cached ? "i/" : "w/");
        diffcore_std(&revs->diffopt);
        diff_flush(&revs->diffopt);
        return 0;

diff --git a/diff-no-index.c b/diff-no-index.c
index 7d68b7f1bef1039b4996e662fb17968c4e3e3e79..b60d3455dae14a7a2cf2daeec8eb47fc7dcd9a09 100644 (file)
--- a/diff-no-index.c
+++ b/diff-no-index.c
@@ -252,6 +252,7 @@ void diff_no_index(struct rev_info *revs,
        if (queue_diff(&revs->diffopt, revs->diffopt.paths[0],
                       revs->diffopt.paths[1]))
                exit(1);
+       diff_set_mnemonic_prefix(&revs->diffopt, "1/", "2/");
        diffcore_std(&revs->diffopt);
        diff_flush(&revs->diffopt);
 

diff --git a/diff.c b/diff.c
index 7b4300a74ab116bdf96ef015322a7533204fd18f..c1804efed930a2d86e77b01241be0422f74c76c4 100644 (file)
--- a/diff.c
+++ b/diff.c
@@ -23,6 +23,7 @@ static int diff_rename_limit_default = 200;
 int diff_use_color_default = -1;
 static const char *external_diff_cmd_cfg;
 int diff_auto_refresh_index = 1;
+static int diff_mnemonic_prefix;
 
 static char diff_colors[][COLOR_MAXLEN] = {
        "\033[m",       /* reset */
@@ -149,6 +150,10 @@ int git_diff_ui_config(const char *var, const char *value, void *cb)
                diff_auto_refresh_index = git_config_bool(var, value);
                return 0;
        }
+       if (!strcmp(var, "diff.mnemonicprefix")) {
+               diff_mnemonic_prefix = git_config_bool(var, value);
+               return 0;
+       }
        if (!strcmp(var, "diff.external"))
                return git_config_string(&external_diff_cmd_cfg, var, value);
        if (!prefixcmp(var, "diff.")) {
@@ -305,6 +310,15 @@ static void emit_rewrite_diff(const char *name_a,
        const char *new = diff_get_color(color_diff, DIFF_FILE_NEW);
        const char *reset = diff_get_color(color_diff, DIFF_RESET);
        static struct strbuf a_name = STRBUF_INIT, b_name = STRBUF_INIT;
+       const char *a_prefix, *b_prefix;
+
+       if (diff_mnemonic_prefix && DIFF_OPT_TST(o, REVERSE_DIFF)) {
+               a_prefix = o->b_prefix;
+               b_prefix = o->a_prefix;
+       } else {
+               a_prefix = o->a_prefix;
+               b_prefix = o->b_prefix;
+       }
 
        name_a += (*name_a == '/');
        name_b += (*name_b == '/');
@@ -313,8 +327,8 @@ static void emit_rewrite_diff(const char *name_a,
 
        strbuf_reset(&a_name);
        strbuf_reset(&b_name);
-       quote_two_c_style(&a_name, o->a_prefix, name_a, 0);
-       quote_two_c_style(&b_name, o->b_prefix, name_b, 0);
+       quote_two_c_style(&a_name, a_prefix, name_a, 0);
+       quote_two_c_style(&b_name, b_prefix, name_b, 0);
 
        diff_populate_filespec(one, 0);
        diff_populate_filespec(two, 0);
@@ -1432,6 +1446,14 @@ static const char *diff_funcname_pattern(struct diff_filespec *one)
        return NULL;
 }
 
+void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b)
+{
+       if (!options->a_prefix)
+               options->a_prefix = a;
+       if (!options->b_prefix)
+               options->b_prefix = b;
+}
+
 static void builtin_diff(const char *name_a,
                         const char *name_b,
                         struct diff_filespec *one,
@@ -1445,9 +1467,19 @@ static void builtin_diff(const char *name_a,
        char *a_one, *b_two;
        const char *set = diff_get_color_opt(o, DIFF_METAINFO);
        const char *reset = diff_get_color_opt(o, DIFF_RESET);
+       const char *a_prefix, *b_prefix;
+
+       diff_set_mnemonic_prefix(o, "a/", "b/");
+       if (DIFF_OPT_TST(o, REVERSE_DIFF)) {
+               a_prefix = o->b_prefix;
+               b_prefix = o->a_prefix;
+       } else {
+               a_prefix = o->a_prefix;
+               b_prefix = o->b_prefix;
+       }
 
-       a_one = quote_two(o->a_prefix, name_a + (*name_a == '/'));
-       b_two = quote_two(o->b_prefix, name_b + (*name_b == '/'));
+       a_one = quote_two(a_prefix, name_a + (*name_a == '/'));
+       b_two = quote_two(b_prefix, name_b + (*name_b == '/'));
        lbl[0] = DIFF_FILE_VALID(one) ? a_one : "/dev/null";
        lbl[1] = DIFF_FILE_VALID(two) ? b_two : "/dev/null";
        fprintf(o->file, "%sdiff --git %s %s%s\n", set, a_one, b_two, reset);
@@ -2308,8 +2340,10 @@ void diff_setup(struct diff_options *options)
                DIFF_OPT_CLR(options, COLOR_DIFF);
        options->detect_rename = diff_detect_rename_default;
 
-       options->a_prefix = "a/";
-       options->b_prefix = "b/";
+       if (!diff_mnemonic_prefix) {
+               options->a_prefix = "a/";
+               options->b_prefix = "b/";
+       }
 }
 
 int diff_setup_done(struct diff_options *options)

diff --git a/diff.h b/diff.h
index 50fb5ddb0bec02b0cd5498d6ecc37d44bf874476..9a679f58f56589b1457bf58ca85c1102af2dade3 100644 (file)
--- a/diff.h
+++ b/diff.h
@@ -160,6 +160,8 @@ extern void diff_tree_combined(const unsigned char *sha1, const unsigned char pa
 
 extern void diff_tree_combined_merge(const unsigned char *sha1, int, struct rev_info *);
 
+void diff_set_mnemonic_prefix(struct diff_options *options, const char *a, const char *b);
+
 extern void diff_addremove(struct diff_options *,
                           int addremove,
                           unsigned mode,